Restorer plants

ABSTRACT

Hybrid cereals are described which are obtained by restoring the pollen fertility for the Pampa cytoplasmic male sterility (P-CMS) and which are characterized by a reduced linkage drag. Plants are provided, in particular rye, which, as the male pollen parent, are capable of restoring the pollen fertility for the P-CMS. Furthermore, the nucleic acid molecule which carries the necessary information for restoring the P-CMS, DNA and vectors which contain such a nucleic acid molecule, corresponding host cells as well as a protein which can be encoded by the nucleic acid molecule and antibodies directed against it are also described. Furthermore, methods for the production of corresponding hybrid plants and transgenic plants are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 16/064,304, filed Jun. 20, 2018, which is a U.S. National Phase of International Patent Application No. PCT/EP2016/082268, filed Dec. 21, 2016, which claims priority to German Patent Application No. 102015016445.7, filed on Dec. 21, 2015.

The entire contents of these applications are incorporated herein by reference in their entirety.

SEQUENCE LISTING

This application contains a Sequence Listing which has been submitted in ASCII format via EFS-Web and is hereby incorporated by reference herein in its entirety. The ASCII text file was created on Jun. 29, 2017, is named Sequence_Listing.txt and is 53,790 bytes in size.

FIELD OF THE INVENTION

The present invention relates to the technical field of plant breeding and green biotechnology, in particular the field of the production of hybrid plants using molecular biological methods, marker technology and genetic engineering. In particular, hybrid cereals are provided which are obtained by restoring pollen fertility for the cytoplasmic male sterility (P-CMS) which is produced by the Pampa cytoplasm, and/or which comprise complete restoration of pollen fertility for the cytoplasmic male sterility (P-CMS) which is produced by the Pampa cytoplasm. They are characterized by the fact that negative, usually yield-reducing effects remain which are otherwise connected with the introgression of chromosomal segments which contain the locus responsible for restoration in cultivars. In this respect, the present invention provides plants, in particular rye plants which, as the male pollen parent, are capable of restoring pollen fertility for the P-CMS whereupon, in hybrid plants from a cross of these pollen parents with a female CMS parent, a linkage drag otherwise coupled with the restoration property is reduced or is even completely eliminated.

Furthermore, the present invention relates to nucleic acid molecules which carry the necessary information for restoration of the P-CMS, DNA and vectors which contain such a nucleic acid molecule, corresponding host cells as well as a protein which can be coded for by the nucleic acid molecule and antibodies directed against it. Furthermore, the invention concerns the use of the nucleic acid molecules, DNA, vectors and antibodies in the production of hybrid plants, for example.

BACKGROUND OF THE INVENTION

Because of its pronounced stress tolerance in nutrient-deficient, dry locations as well as in catchment areas with limited pesticide use, rye exhibits substantial yield advantages compared with barley and wheat, and thus holds specific promise for sustainable agriculture. The use of cytoplasmic male sterility (CMS) in rye, inter alia, has opened up the possibility of breeding hybrid varieties with high yield potentials by exploiting heterosis (Geiger, H. H., and T. Miedaner, “hybrid rye and heterosis.” Genetics and Exploitation of Heterosis in Crops. Crop Science Society. America, Madison, Wis., USA (1999): 439-450). The importance of hybrids in rye as an agricultural cultivation variety in Europe is steadily increasing. In Germany, Denmark or Austria alone, hybrid rye already takes up more than 70% of the total production of rye. In other regions too, in particular in Eastern Europe, in future years there is expected to be a significant increase in hybrid rye cultivation. The main uses for rye are in animal fodder and in bread production, for which the rye is usually mixed with other cereals. Furthermore, rye is gaining increasing significance as a substrate for obtaining bioenergy.

Currently, most hybrid systems in rye are based on exploiting Pampa (P) cytoplasm which, together with non-restorers, mediates male sterility (P-CMS) in the nuclear genome. This was discovered at the end of the 1960s in an Argentinian breed (Geiger, H. H., and F. W. Schnell. “Cytoplasmic male sterility in rye (Secale cereale L.).” Crop Science 10.5 (1970): 590-593). This CMS exhibits excellent stability to environmental conditions and is stably maintained in all European breeding populations in current non-restorer genotypes. The search for efficient restorers for the male fertility of P-CMS, was richly rewarded in primitive rye accessions such IRAN IX, Pico Gentario or Altevogt 14160 (Geiger H H, Miedaner T (1996) Genetic basis and phenotypic stability of male-fertility restoration in rye. Vortr plantszüchtg 35:27-38; Miedaner T, Glass C, Dreyer F, Wilde P, Wortmann H, Geiger H H (2000) Mapping of genes for male fertility restoration in “Pampa” CMS winter rye (Secale cereale L.). Theor Appl Genet 101:1226-1233; Falke K C, Wilde P, Miedaner T (2009) Rye introgression lines as source of alleles for pollen-fertility restoration in Pampa CMS. Plant Breeding 128:528-531). IRAN IX is a self-incompatible rye population which was collected from the Elburz-Karaj region by Kuckuck (1956; Report to the government of Iran on the distribution and variation of cereals in Iran. FAO Report No. 517:1-22) and deposited in the gene bank of the former Bundesforschungsanstalt für Landwirtschaft [Federal Agricultural Research Centre, FAL]. The Pico Gentario accession originates from Argentina and the Altevogt 14160 population also originates from Iran. Both are also self-incompatible and can be obtained from the Botanical Gardens of the Polish Academy of Sciences in Warsaw. Compared with restorer genotypes which originate from central European sources, the restorers from IRAN IX, Pico Gentario or Altevogt 14160 exhibit a high and stable restoration capability. In contrast to current sources from central Europe, this manifests itself in very good pollen shedding, a property which plays a decisive role in minimizing ergot. Ergot infestation is one of the most economically significant diseases of rye (Claviceps purpurea [Fr.] Tul.). As a result, since 2008, the susceptibility of rye varieties to ergot has been officially entered in the variety list of the Federal Plant Variety Office and also by the Polish Plant Variety Office (COBORU) when evaluating rye hybrids. Improving the pollen shedding trait in hybrid varieties, for example with winter rye, by effective restorer loci such as Rfp1, is currently the most effective and sustainable strategy for minimizing the contamination of crops with ergot in hybrid rye. Overall, the introgression of these restorer sources into pollen parent lines constitutes a significant advance for the restoration of fertility in hybrids.

Mapping studies to localise the restorer locus Rfp1 of the donor IRAN IX, Rfp2 of the donor Pico Gentario or the locus from Altevogt 14160 each produced a position on the long arm of chromosome 4R (Miedaner et al. 2000. Mapping of genes for male fertility restoration in “Pampa” CMS winter rye (Secale cereale L.). Theor Appl Genet 101:1226-1233; Stracke et al. 2003. Development of PCR-based markers linked to dominant genes for male-fertility restoration in Pampa CMS of rye (Secale cereale L.), Theor Appl Genet (2003) 106:1184-1190; Falke et al. 2009. Rye introgression lines as source of alleles for pollen-fertility restoration in Pampa CMS. Plant Breeding 128:528-531, Hackauf et al. 2012. Development of COS markers for the Restorer Gene Rfp1 in Rye. Molecular Breeding 30: 1507-1518). Studies with associated selection markers have shown that several restorer genes could possibly be clustered in the region concerned on chromosome 4 RL, or the restorer gene concerned could be an allele of one and the same gene locus (Hackauf et al. (2012) “Development of conserved ortholog set markers linked to the restorer gene Rfp1 in rye.” Molecular breeding 30.3: 1507-1518).

Although the use of the present restorer loci is advantageous on the one hand in view of restoration capability and pollen shedding, on the other hand, the associated introgression segments containing the restorer loci reduce the agronomic performance of today's breeding populations. In particular, the grain yield is so significantly deleteriously affected by the genome region flanking the restorer genes (linkage drag) that the advantage of the heterosis effect in the hybrids is drastically cut down or even completely destroyed. Furthermore, the possibility has also been discussed that the observed linkage drag effect or at least a portion thereof is actually a pleiotropic effect of the restorer gene. Despite intensive backcross studies accompanied by extensive marker development over a period which has now lasted more than ten years, until now, only a coarse genetic position has been determined. By means of continuous selection over more or less closely coupled foreground markers and the target gene, the size of the introgression fragment with the restorer locus has been largely maintained, thus also maintaining a large number of unsuitable donor genes, making the observed linkage drag effect directly plausible. Hackauf et al., (2012) (“Development of conserved ortholog set markers linked to the restorer gene Rfp1 in rye.” Molecular breeding 30.3 (2012): 1507-1518) show for Rfp1 the most up-to-date situation regarding mapping of the genome region of interest around the restorer locus on 4R. By using a comparative approach to gene mapping on the basis of completely decoded grass genomes, they were able to limit the introgression segment including the Rfp1 locus itself to an interval of approximately 2.0 cM, flanked by the markers tc135788 and tc176835, or to an interval of 0.7 cM, flanked by the markers tc256739 and tc300731. However, the restorer gene itself could not be identified, nor until now have substantiated results been obtained regarding the extent and localization of the reduction in agronomic performance. It is also not known to produce recombinants for which the change in the introgression segment and the agronomic performance could be correlated.

The objective of the present invention is therefore to further develop the introgression segments at the basis of the aforementioned restorer loci so that they indeed maintain the desired restoration property, however the reductions in performance are no longer exhibited or are significantly reduced or minimized. In particular, the objective of the invention was to embed, and thus provide, the restorer genes which constitute an essential fundamental of hybrid breeding programs in grasses, preferably in cereals, into high resolution fine mapping of the associated region. Furthermore, in the context of the invention, genotypes should be made available which, with the aid of close-coupled markers around the restorer locus, describe haplotypes for the target region which can be precisely, quantitatively and qualitatively ascribed to the change in agronomic performance. Furthermore, the objective of the invention is to identify markers which are embedded in the restorer gene itself so that with them, the restorer gene can be provided for breeding purposes.

DESCRIPTION OF THE INVENTION

The above objective is achieved by the provision of a plant, in particular from the gramineous order (Poales), which is suitable, as a male pollen parent, for restoring the pollen fertility for the Pampa cytoplasmic male sterility (P-CMS). Preferably, it is a plant from the sweetgrass family (Poaceae) or from the genus Secale or Hordeum and particularly preferably a plant from the species Secale cereale or Hordeum vulgare. The plant is further characterized in that in the plant or in a hybrid plant obtainable from a cross of the plant with a female CMS parent from the same species, a linkage drag effect (see Hackauf et al. 2012) otherwise coupled with the restoration property, preferably a yield-reducing effect, is reduced or completely eliminated. With the aid of the present invention, in this manner, a plant can be provided in which, in the restorer locus, negative unwanted agronomic properties could be decoupled from the restorer genes Rfp1a and Rfp1b. This decoupling means that a high yield can be connected with an efficient restoration capability.

In a particular embodiment, cells of the plants have a cytoplasm which mediates Pampa cytoplasmic male sterility (CMS). Hence, the present invention also provides a hybrid plant with a high yield potential which has a very efficient restoration capability, or a plant which, as a pollen parent, is suitable for restoring pollen fertility for the Pampa cytoplasmic male sterility (CMS), preferably completely. Simultaneously, the linkage drag, which can significantly reduce the agronomic performance, in particular a reduction in yield, is reduced or completely eliminated.

In a preferred embodiment, a plant is provided which comprises a chromosomal segment which comprises at least one nucleic acid molecule which is capable of mediating the restoration property for the Pampa cytoplasmic male sterility. Preferably, the chromosomal segment is an interval between the marker loci tc256739, ctg32 or ctg24met2a5 and tc300731 or 7_01_H_1441 on chromosome 4R from a donor selected from the group consisting of IRAN IX, Pico Gentario and Altevogt 14160. Furthermore, the described chromosomal segment may also be found in other related donors. Such donors can in particular be found in Mediterranean regions, for example Turkey or Spain, having regard to the genetic structure of the chromosomal segment as well as the at least one nucleic acid molecule described herein. In this regard, for example, molecular markers in accordance with the invention such as those described below may be employed. Thus, the present invention is not limited to donors from the group consisting of IRAN IX, Pico Gentario and Altevogt 14160 but, even if not explicitly mentioned, also encompasses more closely related donors which can act as the source of the chromosomal segment in accordance with the invention and of the at least one nucleic acid molecule in accordance with the invention.

Such a chromosomal segment may, for example, be one of the following intervals: between the marker loci tc256739 and tc300731, between the marker loci ctg32 and tc300731, between the marker loci ctg24met2a5 and tc300731, between the marker loci ctg2 and tc300731, between the marker loci ctg16b and tc300731, between the marker loci c40745_1 and tc300731, between the marker loci P20 and tc300731, between the marker loci tc256739 and 7_01_H_1441, between the marker loci ctg32 and 7_01_H_1441, between the marker loci ctg24met2a5 and 7_01_H_1441, between the marker loci ctg2 and 7_01_H_1441, between the marker loci ctg16b and 7_01_H_1441, between the marker loci c40745_1 and 7_01_H_1441, between the marker loci P20 and 7_01_H_1441, between the marker loci tc256739 and 72F13_c2_mTERF, between the marker loci tc256739 and P20, between the marker loci tc256739 and c40745_1, between the marker loci tc256739 and ctg16b, between the marker loci ctg32 and 72F13_c2_mTERF, between the marker loci ctg32 and P20, between the marker loci ctg32 and c40745_1, between the marker loci ctg32 and ctg16b, between the marker loci ctg24met2a5 and 72F13_c2_mTERF, between the marker loci ctg24met2a5 and P20, between the marker loci ctg24met2a5 and c40745_1, between the marker loci ctg24met2a5 and ctg16b, between the marker loci ctg2 and 72F13_c2_mTERF, between the marker loci ctg2 and P20, between the marker loci ctg2 and c40745_1 or between the marker loci ctg2 and ctg16b. Furthermore, the linkage drag effect is preferably that linkage drag effect which was originally coupled with the chromosomal segment from which the restoring nucleic acid molecule originates. Furthermore, the nucleic acid molecule is preferably a nucleic acid molecule which has a nucleotide sequence which codes for a mitochondrial transcription termination factor (mTERF), a homologue, an analogue, an orthologue or a functional fragment thereof. “At least one nucleic acid molecule” may mean one, two, three, four or five nucleic acid molecules; preferably, “at least one nucleic acid molecule” means one or two nucleic acid molecules. The source of the chromosomal segment which comprises at least one nucleic acid molecule which is capable of mediating the restoration property for the Pampa cytoplasmic male sterility may be the primitive rye accessions IRAN IX, Pico Gentario and Altevogt 14160 (Geiger et al., Vortr plantszüchtg 35 (1996), 27-38; Miedaner et al., Theor Appl Genet 101(2000), 1226-1233; Falke et al., Plant Breeding 128 (2009), 528-531). IRAN IX is a self-incompatible rye population from Elburz-Karaj, collected by Kuckuck (FAO Report No. 517 (1956), 1-22) and held in the gene bank of the Bundesforschungsanstalt für Landwirtschaft [Federal Agricultural Research Centre, FAL]. The Pico Gentario accession from Argentina and the Altevogt 14160 population from Iran are also self-incompatible and were both provided by the Botanical Gardens of the “Polish Academy of Sciences” in Warsaw, Poland.

In a particularly preferred embodiment, the at least one nucleic acid molecule has a nucleotide sequence which is selected from the group consisting of: (i) a nucleotide sequence with one of SEQ ID NO: 1 or SEQ ID NO: 28 or a functional fragment thereof, (ii) a nucleotide sequence which codes for an amino acid sequence with one of SEQ ID NO: 2 or SEQ ID NO: 29 or a functional fragment thereof, (iii) a nucleotide sequence which is complementary to a nucleotide sequence in accordance with (i) or (ii), (iv) a nucleotide sequence which hybridizes with a sequence in accordance with (iii) under stringent conditions, (v) a nucleotide sequence which has an identity of at least 70%, 75%, 80%, 85% or 90%, preferably of at least 91%, 92%, 93% 94% or 95%, or particularly preferably of at least 96%, 97%, 98%, 99% or 99.5% with the nucleotide sequence in accordance with (i) or (ii), (vi) a nucleotide sequence which codes for an amino acid sequence which has an identity of at least 65%, 70%, 75%, 80%, 85% or 90%, preferably of at least 91%, 92%, 93% 94% or 95%, or particularly preferably of at least 96%, 97%, 98%, 99% or 99.5% with one of SEQ ID NO: 2 or SEQ ID NO: 29 or a functional fragment thereof, (vii) a nucleotide sequence which codes for an amino acid sequence which, compared with the amino acid sequence shown in SEQ ID NO: 2 or SEQ ID NO: 29, exhibits discrepancies in the amino acid sequence in the form of amino acid deletions, substitutions, additions and/or insertions in the amino acid sequence, preferably of no more than 30%, 25% or 20%, preferably no more than 18%, 16%, 14%, 12% or 10% or particularly preferably no more than 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1% or 0.5% over the entire amino acid sequence. Preferably, the at least one nucleic acid molecule codes for one or more mitochondrial transcription termination factors (mTERF) or a functional fragment thereof. The mTERF protein family shares several important functions with what is known as the pentatricopeptide (PPR) family. Like the mTERF protein family, the pentatricopeptide (PPR) family is also an unusual family of RNA binder proteins which is characterized by degenerate helical repeats. In the PPR family, this consists of approximately 35 amino acids (Small et al., Trends Biochem. Sci. 25 (2000), 46-47), in contrast to the mTERF repeats, which are mainly characterized by approximately 31 amino acids, which form three instead of two helices (Hammani et al., Nucleic Acids Res 42 (2014), 5033-5042). It is not possible to exclude the possibility that the presence of one or more functional PPR genes could have a deleterious effect on the positive effect of the plants described above with improved properties. Thus, the nucleic acid molecule of the plant in one embodiment preferably does not have a functional pentatricopeptide (PPR) gene which originates from the donor.

As described above under (vii), the at least one nucleic acid molecule may code for an amino acid sequence which, compared with the amino acid sequence of SEQ ID NO: 2 or of SEQ ID NO: 29, contains an amino acid sequence with discrepancies in the form of amino acid substitutions, deletions, insertions and/or additions. Preferably, such a nucleic acid molecule is capable of binding to a complementary sequence to SEQ ID NO: 1 or 2 or to SEQ ID NO: 28 or 29 under stringent conditions.

As will be shown in the examples below, close-flanking markers of the Rfp1 gene could be identified and thus close-coupled markers be produced for high resolution mapping of the Rfp1 gene in rye; inter alia, these enabled the restorer gene to be flanked and the Rfp1 target region to be elucidated in cereal genomes. Thus, for the first time, a marker-based transfer of the target gene into new breeding material is possible, such that an efficient selection against the unwanted genetic background of the donor genome is included.

In a preferred embodiment, the chromosomal segment of the plant has one or more of the following marker loci of the donor: ctg2 (amplification product of the primer with SEQ ID NOs: 4 and 5), P20 (amplification product of the primer with SEQ ID NOs: 6 and 7), 72F13_c2_mTERF (amplification product of the primer with SEQ ID NOs: 8 and 9) or ctg16b (amplification product of the primer with SEQ ID NOs: 10 and 11). The restoration property of the plant may also be characterized by the absence of one or more of the following marker loci of the donor: 7_01_H_1441 (amplification product of the primer with SEQ ID NOs: 12 and 13), ctg24met2a5 (amplification product of the primer with SEQ ID NOs: 14 and 15), or ctg32 (amplification product of the primer with SEQ ID NOs: 16 and 17).

In a particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor ctg32, ctg24met2a5, ctg2, ctg16b and c40745_1 (amplification product of the primer with SEQ ID NOs: 18 and 19) and the marker loci of the donor tc256739 (amplification product of the primer with SEQ ID NOs: 21 and 22), 72F13_c2_mTERF, P20, 7_01_H_1441 and tc300731 (amplification product of the primer with SEQ ID NOs: 23 and 24) are absent on the chromosomal segment.

In a further particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor ctg32, ctg24met2a5, ctg2 and ctg16b, and the marker loci of the donor tc256739, c407451, 72F13_c2_mTERF, P20, 7_01_H_1441 and tc300731 are absent on the chromosomal segment.

In a further particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor ctg32, ctg24met2a5 and ctg2, and the marker loci of the donor tc256739, ctg16b, c40745_1, 72F13_c2_mTERF, P20, 7_01_H_1441 and tc300731 are absent on the chromosomal segment.

In a further particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor 72F13_c2_mTERF, P20 and 7_01_H_1441, and the marker loci of the donor tc256739, ctg32, ctg24met2a5, ctg2, ctg16b, c40745_1 and tc300731 are absent on the chromosomal segment.

In a further particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor 72F13_c2_mTERF and P20, and the marker loci of the donor tc256739, ctg32, ctg24met2a5, ctg2, ctg16b, c40745_1, 7_01_H_1441 and tc300731 are absent on the chromosomal segment.

In a further particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor c407451, 72F13_c2_mTERF, P20 and 7_01_H_1441, and the marker loci of the donor tc256739, ctg32, ctg24met2a5, ctg2, ctg16b and tc300731 are absent on the chromosomal segment.

In a further particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor c407451, 72F13_c2_mTERF and P20, and the marker loci of the donor tc256739, ctg32, ctg24met2a5, ctg2, ctg16b, 7_01_H_1441 and tc300731 are absent on the chromosomal segment.

In a further particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor ctg16b, c40745_1, 72F13_c2_mTERF, P20 and 7_01_H_1441, and the marker loci of the donor tc256739, ctg32, ctg24met2a5, ctg2 and tc300731 are absent on the chromosomal segment.

In a further particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor ctg16b, c40745_1, 72F13_c2_mTERF and P20, and the marker loci of the donor tc256739, ctg32, ctg24met2a5, ctg2, 7_01_H_1441 and tc300731 are absent on the chromosomal segment.

In a further particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor ctg2, ctg16b, c40745_1, 72F13_c2_mTERF, P20 and 7_01_H_1441, and the marker loci of the donor tc256739, ctg32, ctg24met2a5 and tc300731 are absent on the chromosomal segment.

In a further particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor ctg2, ctg16b, c40745_1, 72F13_c2_mTERF and P20, and the marker loci of the donor tc256739, ctg32, ctg24met2a5, 7_01_H_1441 and tc300731 are absent on the chromosomal segment.

In a further particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor ctg24met2a5, ctg2, ctg16b, c40745_1, 72F13_c2_mTERF, P20 and 7_01_H_1441, and the marker loci of the donor tc256739, ctg32 and tc300731 are absent on the chromosomal segment.

In a further particularly preferred embodiment, the chromosomal segment of the plant comprises the marker loci of the donor ctg24met2a5, ctg2, ctg16b, c40745_1, 72F13_c2_mTERF and P20, and the marker loci of the donor tc256739, ctg32, 7_01_H_1441 and tc300731 are absent on the chromosomal segment.

In a preferred embodiment, the chromosomal segment is no larger than 190 kb, no larger than 150 kb or no larger than 100 kb, preferably no larger than 75 kb or no larger than 50 kb, particularly preferably no larger than 40 kb, no larger than 30 kb, no larger than 25 kb or no larger than 20 kb. In a particularly preferred embodiment, the chromosomal segment comprises a DNA fragment of 18.425 kb, which preferably has a nucleotide sequence with SEQ ID NO: 20 or a nucleotide sequence which has an identity of at least 85% or 90%, preferably of at least 91%, 92%, 93% 94% or 95%, or particularly preferably of at least 96%, 97%, 98%, 99% or 99.5% with the nucleotide sequence with SEQ ID NO: 20.

In a further preferred embodiment, the nucleic acid molecule does not have a functional pentatricopeptide (PPR) gene which originates from the donor.

The plant of the present invention is preferably an inbred plant, a double haploid plant or a hybrid plant and/or, preferably, homozygous or heterozygous for the restoration property, for the chromosomal segment or the at least one nucleic acid molecule. The hybrid plant may be a “single-cross” hybrid, a “double-cross” hybrid, a “topcross” hybrid, a “three-way-cross” hybrid, a “triple-cross” hybrid, a “composite” hybrid, a “blended” hybrid, a fully restored hybrid, a “second generation” hybrid or another hybrid. Preferably, a plant of the present invention acts as a pollen donor in a hybrid-produced cross and/or in fertilization of grain or seeds on a hybrid plant.

The identification of the restorer genes described in this study as well as the factors responsible for linkage drag was in general carried out in grasses. Preferably, however, the results shown here were obtained in cereals, wherein the plants primarily belong to the genuses rye (Secale), barley (Hordeum) or a cereal species cultivated from rye (first partner) and wheat (second partner) known as Triticale. The negative effect of linkage drag close-coupled to the restorer locus Rfp1 plays a decisive role in hybrid breeding of cereals, in particular such as rye, for example and in rye, as is known, results in substantial reductions in yield. Comparable difficulties are also known for the hybrid breeding of barley. Because of the genetic similarities in the chromosomal region of the restorer locus between rye and barley as well as Triticale, in one embodiment of the present invention, the plant is a plant of the genus Secale, Hordeum or Triticale, preferably a plant of the species Secale cereale or Hordeum vulgare.

In addition to plants with excellent restoration properties and without linkage drag or with reduced linkage drag, the invention also encompasses seeds or descendants of these plants, wherein these comprise the defined chromosomal segment or the at least one defined nucleic acid molecule for the restoration property. Descendants also exhibit the improved restoration property without linkage drag or with reduced linkage drag. Furthermore, organs, parts, tissues or cells of the plant are provided which have the restoration property inherent in them.

The invention also concerns an oligonucleotide, preferably with a maximum length of 50 nucleotides, which has one of the following nucleotide sequences: (i) SEQ ID NOs: 4, 6, 8, 10, 12, 14, 16, 18 or a complement thereof, or (ii) SEQ ID NOs: 5, 7, 9, 11, 13, 15, 17, 19 or a complement thereof. Such oligonucleotides, when used as molecular markers or molecular markers based on such oligonucleotides, are also encompassed by the present invention. Such molecular markers which detect the presence of absence of a marker locus of the donor are, for example, based on a SNP (examples: KASPar or TaqMan markers).

The improvements described above to the chromosomal segment in accordance with the invention which, for example, originates from the donor IRAN IX, come exclusively from the comprehensive and sophisticated development and penetration of the chromosomal segment with molecular markers which are close-coupled to the restoration locus for P-CMS (see markers described above as well as Table 2) and the flanking regions, which presumably carry the agronomically disadvantageous genes (linkage drag). In addition, a fundamental prerequisite is that the markers are suitable for high throughput screening. In the context of the present invention, the production, identification and evaluation of recombinants has been carried out for the first time, although, because of the large genetic distance between the central European elite populations as recipients of the chromosomal segment and the Iranian or Argentinian donor population, the recombination frequency is extraordinarily low. These difficulties are known to the person skilled in the art from the literature (Ruge B, Linz A, Pickering R, Proeseler G, Greif P, Wehling P (2003) Mapping of Rym14^(th), a gene introgressed from Hordeum bulbosum and conferring resistance to BaMMV and BaYMV in barley. Theor Appl Genet 107:965-971).

In addition to the extraordinary advance in the field of genotyping the Rfp1 target region, the present invention also enabled a novel highly diagnostic phenotyping system to be developed. The “Near Isogenic Bulk (NIB)” phenotyping tests (see Example 1 and 2) have for the first time enabled a reliable determination of the linkage drag effect to be made with the required precision, as only in this manner could the linkage drag effect be phenotypically separated from the effects of the genetic background. In this regard, linkage drag effects could be calculated as a difference (Δ_(E-D)) between test crossing means from NIB partners which carry the elite allele (E) and corresponding NIB partners which carry the donor allele (D) for all markers in the chromosomal interval (see also FIG. 2).

In a further aspect, the present invention concerns a method for producing a plant, in particular from the gramineous order (Poales), preferably from the sweet grass family (Poaceae), which is suitable, as a male pollen parent, for restoring the pollen fertility for the P-CMS wherein, in a hybrid plant from a cross with a female CMS parent, a linkage drag otherwise coupled with the restoration property, preferably a yield-reducing effect, is reduced or completely eliminated. Such a method comprises the following step: removal of one or more chromosomal intervals which contain one or more of the following marker loci of the donor: 7_01_H_1441, ctg24met2a5 or ctg32, from the genome of a plant, preferably from chromosome 4R, wherein the inventive chromosomal segment with the Rfp1a gene and/or Rfp1b gene (see also FIG. 1) as described above remains. As an example, the removal of one or more chromosomal intervals may be carried out by genetic recombination during a crossing process between two plants, wherein one plant carries the known Rfp1 locus heterozygously. This conventional breeding technique for the production of a genetic recombination leads to the result that at least one of the donor intervals identified above with linkage drag is replaced by genomic sequences from the recurrent parent which is preferably free from unwanted genes. In this regard, removal may comprise the following steps: (I) crossing a first plant, comprising the restoration locus from a donor selected from the group consisting of IRAN IX, Pico Gentario and Altevogt 14160, with a second plant which does not have this restoration locus; (II) selecting descendants which have the inventive chromosomal segment as described above. Preferably, the selection is marker-based; suitable markers are accessible to the person skilled in the art through the present disclosure. This marker-based selection of the restorer genes can contribute considerably to accelerating the breeding process, because the desired information about the presence of the restorer gene can be acquired early on and without complicated test crossings.

In this regard, the present invention also encompasses a method for detecting a plant, in particular from the gramineous order (Poales), preferably from the sweet grass family (Poaceae), which is suitable, as a male pollen parent, for restoring the pollen fertility for the P-CMS wherein, in a hybrid plant from a cross with a female CMS parent, a linkage drag otherwise coupled with the restoration property, preferably a yield-reducing effect, is reduced or completely eliminated. This method comprises detecting, in the plant, alleles from at least two markers originating from a donor selected from the group consisting of IRAN IX, Pico Gentario and Altevogt 14160, wherein at least one marker is localized on or in the chromosomal interval between tc256739 and ctg2 and at least one marker is localized on or in the chromosomal interval between ctg16b and tc300731, or wherein at least one marker is localized on or in the chromosomal interval between tc256739 and c40745_1 and at least one marker is localized on or in the chromosomal interval between 7_01_H_1441 and tc300731.

Alternatively, the method comprises the detection in the plant of the presence or absence of at least one marker allele originating from a donor selected from the group consisting of IRAN IX, Pico Gentario and Altevogt 14160, on or in the Rfp1 locus, and selection of plants in which the at least one marker allele is present. Preferably, the Rfp1 locus means a chromosomal section between the marker loci tc256739, ctg32 or ctg24met2a5 and tc300731 or 7_01_H_1441 on chromosome 4R from a donor selected from the group consisting of IRAN IX, Pico Gentario and Altevogt 14160. The Rfp1 locus may, for example, be one of the following sections: between the marker loci tc256739 and tc300731, between the marker loci ctg32 and tc300731, between the marker loci ctg24met2a5 and tc300731, between the marker loci ctg2 and tc300731, between the marker loci ctg16b and tc300731, between the marker loci c40745_1 and tc300731, between the marker loci P20 and tc300731, between the marker loci tc256739 and 7_01_H_1441, between the marker loci ctg32 and 7_01_H_1441, between the marker loci ctg24met2a5 and 7_01_H_1441, between the marker loci ctg2 and 7_01_H_1441, between the marker loci ctg16b and 7_01_H_1441, between the marker loci c40745_1 and 7_01_H_1441, between the marker loci P20 and 7_01_H_1441, between the marker loci tc256739 and 72F13_c2_mTERF, between the marker loci tc256739 and P20, between the marker loci tc256739 and c40745_1, between the marker loci tc256739 and ctg16b, between the marker loci ctg32 and 72F13_c2_mTERF, between the marker loci ctg32 and P20, between the marker loci ctg32 and c40745_1, between the marker loci ctg32 and ctg16b, between the marker loci ctg24met2a5 and 72F13_c2_mTERF, between the marker loci ctg24met2a5 and P20, between the marker loci ctg24met2a5 and c40745_1, between the marker loci ctg24met2a5 and ctg16b, between the marker loci ctg2 and 72F13_c2_mTERF, between the marker loci ctg2 and P20, between the marker loci ctg2 and c40745_1 or between the marker loci ctg2 and ctg16b. As an example, for the detection, one or more of the following oligonucleotides which has one of the following nucleotide sequences may be used as a marker: (i) SEQ ID NOs: 4, 6, 8, 10, 12, 14, 16, 18 or a complement thereof, or (ii) SEQ ID NOs: 5, 7, 9, 11, 13, 15, 17, 19 or a complement thereof. In the context of the present invention, by means of the markers described above, recombinant genotypes have been identified and the respective remaining introgression segment has been described: see Example 3. As can be seen in Example 3, the marker P20 plays the most important role in the identification and description, because using it, further marker sequences could be identified and a plurality of marker combinations could be designed; see Table 2 and Example 6.

Alternatively, modern biotechnology offers the person skilled in the art a variety of further tools which enable precise genome engineering to be carried out: genetic engineering approaches with the aid of which the elimination of linkage drag-carrying nucleotide sequences from a plant genome can be supported or directly obtained, comprise the use of TALE nucleases (TALENs) or zinc finger nucleases (ZFNs) as well as CRISPR/Cas systems which, inter alia, have been described by way of example in German patent document DE 10 2013 014 637 for the elimination of linkage drag-carrying nucleotide sequences from the genome of Helminthosporium turcicum-resistant (hybrid) maize; see DE 10 2013 014 637 on pages 13 and 14 in paragraphs [0038] to [0042] and the references cited therein. These techniques, which are also described in international patent application WO 2014/104878, may be used in an equivalent manner in the production of the present plants in accordance with the invention.

The present invention also encompasses a combination of the conventional breeding technique and modern biotechnology. Thus, for example, with the aid of this novel genome editing approach, recombination “hot spots” can be produced in a plant which occur at suitable sites for directly promoting the removal of linkage drag. Thus, the present invention provides the person skilled in the art with the necessary information regarding localization of the linkage drag as well as the position of the restoration gene/restoration genes.

Furthermore, the novel genome editing approaches also allow for direct introduction of the chromosomal segment in accordance with the invention with reduced or entirely eliminated linkage drag. In this regard, this invention also encompasses a further method for the production of a plant in accordance with the invention, in particular from the gramineous order (Poales), preferably from the sweet grass family (Poaceae), which is suitable, as a male pollen parent, for restoring the pollen fertility for the Pampa cytoplasmic male sterility (CMS) wherein, in a hybrid plant from a cross with a female CMS parent, a linkage drag otherwise coupled with the restoration property, preferably a yield-reducing effect, is reduced or completely eliminated. Such a method comprises the following steps: (I) providing a portion of a plant which preferably does not carry the restoration locus of the present invention, as the target structure containing the target nucleic acid region, preferably a genomic DNA which corresponds to the chromosomal positioning of that of the Rfp1 locus; (II) providing one or more recombinant constructs which together comprise or code for the components of the genome editing tool; (III) providing at least one vector for introducing the recombinant construct/constructs; (IV) providing at least one further recombinant construct comprising the inventively defined nucleic acid molecule, the recombinant DNA, the expression cassette or the chromosomal segment for targeted homology-directed repair of the target nucleic acid region in the target plant structure or insertion into the target nucleic acid region in the target plant structure; (V) introducing the recombinant constructs from (II) and (IV) into the target plant structure; (VI) cultivating the target plant structure under conditions which activate the components of the genome editing tool and thereby allow a targeted modification to be carried out in the target nucleic acid region in the target plant structure, in order to obtain a target plant structure comprising at least one cell which comprises the targeted modification of the target nucleic acid region; and (VII) regenerating a plant from the at least one cell.

In a further aspect, the present invention concerns a method for the production of an inventive hybrid plant, preferably from the gramineous order (Poales), particularly preferably from the sweet grass family (Poaceae) or from the genus Secale or Hordeum and more particularly preferably from the species Secale cereale or Hordeum vulgare. This method comprises, in a first step (1), the method for the production of a plant which is capable, as a male pollen parent, of restoring the pollen fertility for the Pampa cytoplasmic male sterility (CMS), as defined in the preceding paragraphs. In a further step (2) of this method, the plant produced in step (1) or a descendant thereof, which still comprises the inventive chromosomal segment or the inventive nucleic acid molecule, is crossed as a male pollen parent with a female CMS parent, preferably from the same species. In this case, the male pollen parent and/or the female CMS parent is preferably a double haploid plant, an inbred plant, a CMS single cross or what is known as a pollen parent synthetic. In a step (3), the hybrid seed is harvested from the female CMS parent. An optional step (4) comprises sowing the hybrid seed in order to produce the hybrid plant and further optional steps (5) comprise harvesting the seed from the hybrid plant and (6) sowing the seed from the hybrid plant. Furthermore, the present invention encompasses seed or seeds and plants or hybrid plants which are obtained or can be obtained using the above method.

In a further aspect, the present invention also concerns nucleic acid molecule which is suitable for mediating the restoration property with reduced or completely eliminated linkage drag, wherein the nucleic acid molecule comprises a nucleotide sequence which is selected from the group consisting of: (i) a nucleotide sequence with one of SEQ ID NO: 1 or SEQ ID NO: 28 or a functional fragment thereof, (ii) a nucleotide sequence which codes for an amino acid sequence with one of SEQ ID NO: 2 or SEQ ID NO: 29 or a functional fragment thereof, (iii) a nucleotide sequence which is complementary to a nucleotide sequence in accordance with (i) or (ii), (iv) a nucleotide sequence which hybridizes with a sequence in accordance with (iii) under stringent conditions, (v) a nucleotide sequence which has an identity of at least 70%, 75%, 80%, 85% or 90%, preferably of at least 91%, 92%, 93% 94% or 95%, or particularly preferably of at least 96%, 97%, 98%, 99% or 99.5% with the nucleotide sequence in accordance with (i) or (ii), (vi) a nucleotide sequence which codes for an amino acid sequence which has an identity of at least 65%, 70%, 75%, 80%, 85% or 90%, preferably of at least 91%, 92%, 93% 94% or 95%, or particularly preferably of at least 96%, 97%, 98%, 99% or 99.5% with the SEQ ID NO: 2 or a functional fragment thereof, (vii) a nucleotide sequence which codes for an amino acid sequence which, compared with the amino acid sequence shown in SEQ ID NO: 2 or SEQ ID NO: 29, exhibits discrepancies in the amino acid sequence in the form of amino acid deletions, substitutions, additions and/or insertions in the amino acid sequence, preferably of no more than 30%, 25% or 20%, preferably no more than 18%, 16%, 14%, 12% or 10% or particularly preferably no more than 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1% or 0.5% over the entire amino acid sequence. Because of the exact identification and fine mapping of the restoration property of the restorer locus Rfp1, it is also possible to use the nucleic acid molecule defined above in other ways in order to obtain the improved properties of the plant. For this reason, the present invention also encompasses an expression cassette, recombinant DNA or vectors which each comprise the nucleic acid molecule.

In one embodiment, the nucleic acid molecule is comprised by a recombinant DNA. In this case, as a rule, a promoter and/or other transcription or translation control elements will be included in it or associated with it. The promoters used will primarily be promoters which allow transcription of the DNA only in prescribed cells. In addition to the promoters, there are a plurality of further transcription control elements such as, for example, enhancers, operators, repressors and transcription termination signals, although this is not limiting, which are functionally connected to the DNA, in order to produce a targeted cell-specific transcription. Promoters and other transcription regulation elements are generally known and accessible to the person skilled in the art in the prior art; see, for example, WO 00/75359 on page 23, line 5 to page 24, line 17.

The vector may be a plasmid, a cosmid, a phage or an expression vector, a transformation vector, shuttle vector or cloning vector; it may be double or single-stranded, linear or circular, or it may transform a prokaryotic or eukaryotic host either by integration into its genome or extrachromosomally. Preferably, the nucleic acid molecule in accordance with the invention is operatively connected to one or more regulatory sequences which allow the transcription and, optionally, expression in a prokaryotic or eukaryotic host cell; see, for example, Sambrook et al., Molecular Cloning: A Laboratory Manual 3rd Ed. Cold Spring Harbor Laboratory Press. Cold Spring Harbor, N.Y., 2001 and the international application WO 00/75359 on page 21, line 20 to page 22, line 32. A regulatory sequence, preferably DNA, may be homologous or heterologous to the nucleic acid in accordance with the invention. The nucleic acid may, for example, be under the control of a suitable promoter or a terminator. Suitable promoters may be promoters which are constitutively induced (for example: 35S promoter from the “Cauliflower mosaic virus” (Odell et al. 1985), which are tissue-specific, stress-specific or development-specific (for example: anther-specific expression). Suitable promoters may also be synthetic or chimeric promoters which do not occur in nature, composed of a plurality of elements and containing a minimal promoter as well as at least one cis-regulatory element upstream of the minimal promoter which acts as a binding site for special transcription factors. Chimeric promoters can be designed to desired specifications and are induced or re-primed by various factors. Examples of such promoters can be found in Gurr & Rushton (Gurr, S J; Rushton, P J. Engineering plants with increased disease resistance: what are we going to express? Trends in Biotechnology, 2005, 23. Jg., No. 6, p. 275-282) or Venter (Synthetic promoters: genetic control through cis engineering. Trends in Plant Science, 2007, 12. Jg., No. 3, p. 118-124). An example of a suitable terminator is the nos-terminator (Depicker, A, Stachel, S, Dhaese, P, Zambryski, P and Goodman, H (1982) J. Mol. Appl. Genet., 1, 561-575).

In addition to the vectors described above, the present invention also provides a method which comprises introducing the described vector into a host cell. The vector may, for example, be introduced by conjugation, mobilization, biolistic transformation, agrobacterium-induced transformation, transfection, transduction, vacuum filtration or electroporation. Such methods as well as methods for the preparation of the described vectors are familiar to the person skilled in the art (Sambrook et al. 2001, Molecular cloning: a laboratory manual (3-volume set) (Vol. 999). Cold Spring Harbor, New York: Cold Spring Harbor Laboratory Press). Furthermore, the prior art contains various methods by means of which transgenic plants can be produced and the restoration trait can be introduced. These include direct and indirect methods. The methods encompass particle bombardment (Weeks et al. Plant Physiol. 102, (1993) 1077-1084; Vasil et al., Bio/Technology 10 (1992), 662-674), agrobacterium transformation (Chan et al., Plant Mol. Biol. 22 (1993), 491-506), electroporation of regeneratable tissue (Shillito et al. 1985 “High efficiency direct gene transfer to plants.” Nature Biotechnology 3.12: 1099-1103), silicon carbide-mediated gene transfer (Dalton et al., Plant Sci. 132 (1998), 31-43) and protoplast-mediated gene transfer (Shimamoto et al., Nature, 338 (1989), 274-276), biolistic or agrobacterium-mediated gene transfer (WO 01/73084). Introduction of the restoration trait may also be carried out by introgression (Harper et al., Annals of Botany 107: (2011), 1313-1320) or also by means of a genetic engineering strategy. Many novel genetic engineering methods for introducing DNA and also for inactivating genomic sequences are known to the person skilled in the art (for example the genome editing method based zinc finger nucleases, TALENs or on a CRISPR/Cas system).

Alternatively or in addition, the present invention also concerns host cells which comprise the nucleic acid molecule as a transgene, expression cassette, recombinant DNA as a transgene or the vector as described above. A “host cell” in the context of the invention may be a prokaryotic (for example bacterial) or eukaryotic cell (for example a plant cell or a yeast cell). Preferably, the host cell is an agrobacterium such as Agrobacterium tumefaciens or Agrobacterium rhizogenes or a plant cell which comprises the nucleic acid molecule, the expression cassette, the recombinant DNA or the vector of the present invention. The person skilled in the art will be aware of both many methods such as conjugation or electroporation, with which the nucleic acid molecule, the expression cassette, the recombinant DNA or the vector of the present invention can be introduced into an agrobacterium, as well as methods such as various transformation methods (biolistic transformation, agrobacterium-mediated transformation), with which the nucleic acid molecule, the expression cassette, the recombinant DNA or the vector of the present invention can be introduced into a plant cell (Sambrook et al. 2001).

By identifying the restoration mediating genes, it is also possible to use it in transgenic plants wherein linkage drag associated with them can be reduced to a minimum. In this manner, the invention also encompasses the provision of a transgenic plant or seeds thereof which comprise a plant cell as defined above. An example of such a transgenic plant cell or plant is a plant cell or plant which is transformed, preferably in a stable manner, with the inventive nucleic acid molecule, with the expression cassette, with the recombinant DNA or with the vector of the present invention. The transgenic plant has a newly-mediated restoration property for pollen fertility for the Pampa cytoplasmic male sterility (CMS) or an improved restoration property for the pollen fertility for the Pampa cytoplasmic male sterility (CMS) compared with a wild type plant which is isogenic but does not have the inventive nucleic acid molecule, with the expression cassette, with the recombinant DNA or with the vector of the present invention. Preferably, these transgenic plants additionally have a newly-mediated resistance to a pathogen, preferably to a fungus, in particular to the fungus Claviceps purpurea (Fr.), or an enhanced resistance to a pathogen, preferably to a fungus, in particular to the fungus Claviceps purpurea (Fr.), compared with a wild type plant which is isogenic, but not transformed with the inventive nucleic acid molecule, with the expression cassette, with the recombinant DNA or with the vector of the present invention, preferably in a stable manner.

In addition to the nucleic acid molecule which codes for the restoration property with reduced or completely eliminated linkage drag, the present invention further concerns an mTERF protein or homologue, analogue, orthologue or a functional fragment thereof which can be coded by the nucleic acid molecule as well as an antibody which specifically binds to the mTERF protein or homologue, analogue, orthologue or a functional fragment thereof. The mTERF protein preferably comprises an amino acid sequence with one of SEQ ID NO: 2 or SEQ ID NO: 29 or an amino acid sequence which has an identity of at least 65%, 70%, 75%, 80%, 85% or 90%, preferably of at least 91%, 92%, 93% 94% or 95%, or particularly preferably of at least 96%, 97%, 98%, 99% or 99.5% with the SEQ ID NO: 2 or SEQ ID NO: 29. Furthermore, the present invention also concerns an antibody which specifically binds to the mTERF protein. The recombinant production of proteins and functional fragments thereof is familiar to the person skilled in the art and has been described, for example, in Sambrook et al. (Molecular Cloning: A Laboratory Manual 3rd Ed. Cold Spring Harbor Laboratory Press. Cold Spring Harbor, N.Y., 2001 Wingfield, P. T. 2008. Production of Recombinant proteins. Current Protocols in Protein Science. 52:5.0:5.0.1-5.0.4). Polyclonal or monoclonal antibodies to the protein of the present invention may be produced by the person skilled in the art using known methods such as those described by E. Harlow et al. (Antibodies: A Laboratory Manual (1988)). The production of monoclonal antibodies as well as of Fab- and F(ab′)₂ fragments, which are also useful in protein detection methods, may be carried out using various conventional methods as described by Goding (Mononoclonal Antibodies: Principles and Practice, p. 98-118, New York: Academic Press (1983)).

The use of antibodies for the production and selection of hybrid plants or transgenic plants with an enhanced yield have, for example, been described in the international patent application WO 2011/061656 in paragraphs [00678] and [00847] and the references cited therein. These techniques may equally be used in the production of the plants of the present invention.

In a further aspect, the present invention provides a method for producing a plant, in particular from the gramineous order (Poales), which is suitable, as a male pollen parent, for restoring the pollen fertility for the Pampa cytoplasmic male sterility (CMS). Such a method comprises the following steps: A) mutagenizing plant cells or portions of a plant and subsequently regenerating plants from the mutated plant cells or mutagenized portions or mutagenizing plants, and B) identifying a plant from A) which comprises an endogenous DNA sequence which is identical to a nucleic acid sequence selected from the group consisting of: (i) the nucleotide sequence with one of SEQ ID NO: 1 or SEQ ID NO: 28 or a functional fragment thereof, (ii) the nucleotide sequence which codes for an amino acid sequence with one of SEQ ID NO: 2 or SEQ ID NO: 29 or a functional fragment thereof, (iii) the nucleotide sequence which is complementary to a nucleotide sequence in accordance with (i) or (ii), (iv) the nucleotide sequence which hybridizes with a sequence in accordance with (iii) under stringent conditions, (v) the nucleotide sequence which has an identity of at least 70%, 75%, 80%, 85% or 90%, preferably of at least 91%, 92%, 93% 94% or 95%, or particularly preferably of at least 96%, 97%, 98%, 99% or 99.5% with the nucleotide sequence in accordance with (i) or (ii), (vi) the nucleotide sequence which codes for an amino acid sequence which has an identity of at least 65%, 70%, 75%, 80%, 85% or 90%, preferably of at least 91%, 92%, 93% 94% or 95%, or particularly preferably of at least 96%, 97%, 98%, 99% or 99.5% with SEQ ID NO: 2 or a functional fragment thereof, (vii) the nucleotide sequence which codes for an amino acid sequence which, compared with the amino acid sequence shown in SEQ ID NO: 2 or SEQ ID NO: 29, exhibits discrepancies in the amino acid sequence in the form of amino acid deletions, substitutions, additions and/or insertions in the amino acid sequence, preferably by no more than 30%, 25% or 20%, preferably no more than 18%, 16%, 14%, 12% or 10% or particularly preferably no more than 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1% or 0.5% over the entire amino acid sequence, or which has at least one mutation in a regulatory sequence of the endogenous DNA sequence which acts so that the identified plant has a newly-mediated restoration property for the pollen fertility for the Pampa cytoplasmic male sterility (CMS) or an improved restoration property for the pollen fertility for the Pampa cytoplasmic male sterility (CMS) compared with a non-mutated wild type plant which is otherwise isogenic and/or which has a newly-mediated resistance against a pathogen, preferably against a fungus, in particular against the fungus Claviceps purpurea (Fr.), or an enhanced resistance against a pathogen, preferably against a fungus, in particular against the fungus Claviceps purpurea (Fr.) compared with a non-mutated wild type plant which is otherwise isogenic.

Preferably, the endogenous DNA sequence from step B) codes for an mTERF protein, particularly preferably for the mTERF protein with one of SEQ ID NOs: 2 or SEQ ID NO: 29 or a homologue, analogue or orthologue thereof. Preferably, the regulatory sequence of the endogenous DNA sequence from step B) is a promoter or a portion thereof. An example of a regulatory sequence of the endogenous DNA sequence is the promoter with SEQ ID NO: 3.

A “mutation” means a modification on a DNA level, i.e. a change in the genetics and/or epigenetics. As an example, a modification in the genetics may be the exchange of at least one nucleobase in the endogenous DNA sequence or in a regulatory sequence of the endogenous DNA sequence. If such a nucleobase exchange occurs, for example in a promoter, then this may result in a modified activity of the promoter because, for example, cis-regulatory elements are modified in a manner such that the affinity of a transcription factor to the mutated cis-regulatory element is modified compared with the wild type promoter, so that the activity of the promoter with the mutated cis-regulatory element is raised or reduced, depending on whether the transcription factor is a repressor or inductor or whether the affinity of the transcription factor to the mutated cis-regulatory element is strengthened or weakened. If such a nucleobase exchange occurs, for example in a coding region or the endogenous DNA sequence, this may lead to an amino acid exchange in the encoded protein, which may result in an alteration in the activity or stability of the protein compared with the wild type protein. Possible amino acid exchanges can be discerned by comparing the amino acid sequences. FIG. 9 shows a comparison of the wild type sequence of rfp1a (SEQ ID NO: 33) with that of the restoration property-mediating amino acid sequence from IRAN9 (SEQ ID NO: 29). As an example, the following potential amino acid exchanges may be derived: in position 10 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises an alanine (A) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises a threonine (T), at position 18 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises a proline (P) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises a threonine (T), at position 43 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises a glutamine (Q) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises an aspartic acid (D), at position 45 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises a glutamic acid (E) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises an aspartic acid (D), at position 62 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises a threonine (T) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises an alanine (A), at position 63 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises an alanine (A) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises a threonine (T), at position 108 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises a glutamic acid (E) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises an aspartic acid (D), at position 126 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises a serine (S) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises an alanine (A), at position 193 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises an aspartic acid (D) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises a glycine (G), at position 213 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises a glycine (G) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises a glutamic acid (E), at position 243 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises a serine (S) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises a cysteine (C), at position 272 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises a cysteine (C) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises an arginine (R), at position 276 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises an alanine (A) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises a threonine (T), at position 303 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises an isoleucine (I) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises a valine (V), at position 363 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises an alanine (A) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises a valine (V), or at position 365 of SEQ ID NO: 29, at which the restoration property-mediating mTERF protein comprises a histidine (H) and a corresponding (non-restoring protein) from the wild type (SEQ ID NO: 33) comprises an arginine (R). In an analogous manner, potential amino acid exchanges may also be deduced from FIG. 10, which shows a comparison of the wild type amino acid sequences of rfp1b (SEQ ID NO: 31) with that of the restoration property-mediating amino acid sequence from IRAN9 (SEQ ID NO: 2). Further potential mutations as modifications on a DNA level (for example in the form of nucleotide exchanges or insertions/deletions) may also be deduced in an analogous manner from comparisons of the coding nucleotide sequences of rfp1a and rfp1b in FIGS. 7 and 8.

A further example of a modification in the genetics is the deletion of nucleotides in the regulatory sequence and/or the endogenous DNA sequence as well as the addition of nucleotides in the regulatory sequence and/or in the endogenous DNA sequence. An example of the regulation of genes by insertion of nucleotides by means of transposon mutagenesis in maize is shown by Das & Martienssen (Das, Lekha, and Robert Martienssen. “Site-selected transposon mutagenesis at the hcf106 locus in maize.” The Plant Cell 7.3 (1995): 287-294.). A modification to the epigenetics may, for example, be accomplished by means of a modified methylation pattern for the DNA.

The person skilled in the art is aware how a “mutation” within the meaning of the invention can be obtained by means of the mutagenization process in step A) of the method for the production of a plant cell/plant. The mutagenization here includes both conventional mutagenesis and also site-specific mutagenesis or “genome editing”. In conventional mutagenesis, a modification on the DNA level is not carried out in a targeted manner. The plant cell or plant is exposed to mutagenetic conditions such as, for example, by TILLING using UV light irradiation or using chemical materials (Till, Bradley J., et al. “Discovery of induced point mutations in maize genes by TILLING.” BMC Plant Biology 4.1 (2004): 12.). A further method for carrying out random mutagenesis is mutagenesis with the aid of a transposon.

Site-specific mutagenesis enables modifications on a DNA level to be deliberately introduced to predetermined sites in the DNA. Examples which may be used in this regard are TALENS (WO 2010/079430, WO 2011/072246), meganucleases (Silva, George, et al. “Meganucleases and other tools for targeted genome engineering: perspectives and challenges for gene therapy.” Current gene therapy 11.1 (2011): 11.), homing endonucleases (Stoddard, Barry L. “Homing endonucleases: from microbial genetic invaders to reagents for targeted DNA modification.” Structure 19.1 (2011): 7-15.), zinc finger nucleases (Lloyd, Alan, et al. “Targeted mutagenesis using zinc-finger nucleases in Arabidopsis.” Proceedings of the National Academy of Sciences of the United States of America 102.6 (2005): 2232-2237), or a CRISPR/Cas-system (Gaj, Thomas, Charles A. Gersbach, and Carlos F. Barbas. “ZFN, TALEN, and CRISPR/Cas-based methods for genome engineering.” Trends in biotechnology 31.7 (2013): 397-405.). As an example, the mutation occurs in all copies or alleles or where appropriate in all homologues of the corresponding endogenous DNA sequences. In respect of a diploid organism such as, for example, Secale cereale or Hordeum vulgare, this may typically mean at least two modifications.

The identification of a plant in step B) may, for example, be carried out with the aid of molecular markers or probes. DNA probes are, for example, primers or primer pairs which can be used in a PCR reaction. As an example, Tilling mutants can be detected or identified by sequencing the target gene in a TILLING population or other methods which detect mispairing in the DNA such as, for example, melting point analyses or the use of mispairing-specific nucleases. Thus, the present invention encompasses primer/primer pairs, such as primers for detecting mTERF or a mutated form thereof. Furthermore, mutants produced by means of transposons may be detected by using transposon-specific primers and target gene-specific primers in the PCR over the whole population and subsequent sequencing of PCR products, Such primers are also encompassed by the present invention. Mutation-determined modification of the expression rate or the degree of expression may, for example, be determined using RT-PCR in plant tissues, a mutation-determined modification to the stability by testing with ubiquitin binding sites, for example, and predicting modifications in the tertiary structure. Furthermore, recombinant expression of the wild type proteins and the corresponding mutated proteins and biochemical activity tests are suitable. The person skilled in the art will be aware of other methods and means in the prior art which can be used to identify a plant or plant cell in step B).

The present invention also concerns molecular markers which detect the presence or absence of a mutation in the endogenous DNA sequence or in a regulatory sequence of the endogenous DNA sequence. Such markers are based, for example, on an SNP and are specific for the mutation (examples: KASP or TaqMan marker). Examples of suitable SNPs for marker development for Secale cereale can be found in the sequence comparison of FIGS. 7 and 8.

The present invention also concerns a plant which can be produced or is produced by the present method, or a portion of this plant. Similarly, the present invention also encompasses a descendant of the plant which has the at least one mutation and thus a newly-mediated restoration property for the pollen fertility for the Pampa cytoplasmic male sterility (CMS) or an improved restoration property for the pollen fertility for the Pampa cytoplasmic male sterility (CMS) compared with a non-mutated wild type plant which is otherwise isogenic, and/or which has a newly-mediated resistance against a pathogen, preferably against a fungus, in particular against the fungus Claviceps purpurea (Fr.), or an enhanced resistance against a pathogen, preferably against a fungus, in particular against the fungus Claviceps purpurea (Fr.) compared with a non-mutated wild type plant which is otherwise isogenic.

In a farther aspect, the present invention provides a method for producing a transgenic plant which has a newly-mediated restoration property for the pollen fertility for the Pampa cytoplasmic male sterility (CMS) or an improved restoration property for the pollen fertility for the Pampa cytoplasmic male sterility (CMS) compared with a non-mutated wild type plant which is otherwise isogenic, and/or which has a newly-mediated resistance against a pathogen, preferably against a fungus, in particular against the fungus Claviceps purpurea (Fr.), or an enhanced resistance against a pathogen, preferably against a fungus, in particular against the fungus Claviceps purpurea (Fr.) compared with a non-mutated wild type plant which is otherwise isogenic. The method may comprise the following steps: A) providing the nucleic acid molecules, the expression cassette or the recombinant DNA described above, or providing the vector described above, B) transformation, preferably stable transformation, of at least one plant cell by introducing the nucleic acid molecule, the expression cassette, the recombinant DNA or the vector from A), C) regenerating transgenic plants from the at least one transformed plant cell from B), and optionally D) identification of a plant which has a newly-mediated restoration property for the pollen fertility for the Pampa cytoplasmic male sterility (CMS) or an improved restoration property for the pollen fertility for the Pampa cytoplasmic male sterility (CMS) compared with a non-mutated wild type plant which is otherwise isogenic, and/or which has a newly-mediated resistance against a pathogen, preferably against a fungus, in particular against the fungus Claviceps purpurea (Fr.), or an enhanced resistance against a pathogen, preferably against a fungus, in particular against the fungus Claviceps purpurea (Fr.) compared with a non-mutated wild type plant which is otherwise isogenic, from C). The method for the production of the transgenic plant also encompasses the provision of two or more of the nucleic acid molecules described above, optionally also different embodiments of the nucleic acid molecule in accordance with the invention and optionally in one or more expression cassettes or vectors, and transformation of plant cells by introduction of the two or more nucleic acid molecules.

The present invention also concerns a transgenic plant which can be produced or is produced using said method, or a portion of this plant. Similarly, the present invention also encompasses a descendant of the transgenic plant which has a newly-mediated restoration property for the pollen fertility for the Pampa cytoplasmic male sterility (CMS) or an improved restoration property for the pollen fertility for the Pampa cytoplasmic male sterility (CMS) compared with a non-mutated wild type plant which is otherwise isogenic, and/or which has a newly-mediated resistance against a pathogen, preferably against a fungus, in particular against the fungus Claviceps purpurea (Fr.), or an enhanced resistance against a pathogen, preferably against a fungus, in particular against the fungus Claviceps purpurea (Fr.) compared with a non-mutated wild type plant which is otherwise isogenic.

In a further aspect, the present invention concerns a method for mediating or increasing the restoration property for the pollen fertility for the Pampa cytoplasmic male sterility (CMS) in a plant cell or a plant and/or for mediating or increasing the resistance against a pathogen, preferably against a fungus, in particular against the fungus Claviceps purpurea (Fr.). Such a method may comprise the following steps: A) transformation, preferably stable transformation, of at least one plant cell by introducing the inventive nucleic acid molecules, the recombinant DNA or the expression cassette of the present invention described above, or the vector of the present invention described above, optionally B) regenerating transgenic plants from the at least one transformed plant cell from A). The method for the production of the transgenic plant cell/plant also encompasses the transformation of two or more of the inventive nucleic acid molecules described above, optionally also different embodiments of the inventive nucleic acid molecule and optionally one or more expression cassettes or vectors of the present invention.

Furthermore, the present invention concerns the use of the plant described above, the descendant described above or said transgenic plant for the production of a hybrid plant in accordance with the invention or a transgenic plant in accordance with the invention, preferably from the genus Secale or Triticale, preferably a plant of the species Secale cereale, in which its pollen fertility for the Pampa CMS has been restored and/or which has an enhanced resistance against a fungal pathogen, in particular against the fungus Claviceps purpurea (Fr.).

Furthermore, the entities described above such as oligonucleotides, nucleic acids, expression cassettes, recombinant DNA, vectors and antibodies may also be of use in the production of the plant or the transgenic plant. In this regard, the present invention also encompasses the use of the oligonucleotide described above, the nucleic acid molecule, the recombinant DNA, the vector or the antibody in the production of a hybrid plant in accordance with the invention or of a transgenic plant in accordance with the invention. In a preferred embodiment, the hybrid plant is selected from the genus Secale or Triticale, preferably a plant of the species Secale cereale, in which its pollen fertility for the Pampa CMS has been restored and/or which has an enhanced resistance against a fungal pathogen, in particular against the fungus Claviceps purpurea (Fr.). In particular, the oligonucleotides and nucleic acids as well as recombinant DNA, vectors and antibodies may also be of use in the production of a transgenic plant.

In a further aspect, the present invention concerns the use of a nucleic acid molecule which codes for an mTERF protein, or of encoded mTERF proteins in a plant, in particular from the gramineous order (Poales), preferably from the sweet grass family (Poaceae), in order to restore a cytoplasmic male sterility (CMS), in particular the Pampa CMS. Preferably, restoration is carried out by crossing the plant containing the nucleic acid molecule as a paternal parent with a second plant, preferably from the same species, containing the CMS cytoplasm. Preferably, the nucleic acid molecule is the nucleic acid molecule in accordance with the invention described above, which is capable of mediating the restoration property, or in the case of the mTERF protein, it is the mTERF protein in accordance with the invention.

Further embodiments and advantages of the present invention will become apparent from the detailed description, figures and the examples.

First of all, some of the terms used in this application will be defined in more detail below: The term “allele” should be understood to mean two or more different nucleotide sequences which are located at a specific gene locus on a chromosome. A first allele is on one chromosome, a second on a second chromosome at the same position. If the two alleles are different, they are heterozygous, and if the alleles are the same, they are homozygous. Different alleles of a gene (gene alleles) differ in at least one SNP (single nucleotide polymorphisms). Depending on the context of the description, an “allele” also means only a single SNP which, for example, allows a distinction between the donor of RFP1 and recurrent parents. Different gene alleles can also be detected by using markers. Such gene alleles at a specific locus are also known as “marker alleles”. Depending on the context of the description, a “marker locus” should also be understood to mean a marker allele at a specific locus.

The expressions “chromosome fragment”, “chromosome segment” as well as variations in the terms such as “chromosomal segment” or “chromosomal fragment”, unless otherwise stated, are equivalent and describe a specific chromosomal DNA section of a specific chromosome which comprises at least one gene. An “integrated chromosomal fragment” thus originates from a donor source. In the context of the invention, the sequential succession of genes within an integrated chromosomal fragment corresponds to that sequence that is present in the original chromosomal fragment of the donor source. A chromosomal fragment or a portion thereof may constitute a specific “haplotype”, wherein the chromosomal fragment then comprises specific SNPs through which the haplotype is uniquely specified and can be identified.

The terms “distal” and “proximal” describe the position of a chromosomal interval or a genetic fragment in relation to a specific reference location (for example a specific polynucleotide, another chromosomal interval or a gene) on a whole chromosome, wherein “distal” means that the interval or the section is located on the side of the reference location away from the chromosome centromer, and “proximal” means that the interval or the section is located on the side of the reference location which is facing the chromosome centromer.

The terms “coupled”, “close-coupled” or “close-flanking” should be understood to mean that two loci (for example two genetic sections or two markers (marker loci or marker alleles)) on a gene map are less than 2 cM, less than 1 cM, less than 0.5 cM, less than 0.2 cM, less than 0.1 cM, less than 0.05 cM or less than 0.01 cM apart from each other.

The term “yield” in the context of the present invention concerns the productivity per unit area of a specific plant product with commercial value. As an example, the “yield” of rye is usually measured in metric tonnes of seed or grain per hectare (ha) and season or in metric tonnes of dry biomass per hectare (ha) and season. Unless stated otherwise, or specified otherwise, the “yield” may refer to the absolute fresh or dry matter, the relative fresh or dry matter, the silage yield (also Total Dry Matter) or the grain yield. The yield is influenced by genetic and environmental factors and is principally a combination of many agronomic properties which are based on traits of a plant which are based on general elements and which, over the season, contribute to the final yield. Examples of these individual agronomic properties are vegetative vitality, stress tolerance, disease resistance or tolerance, herbicide resistance, tillering tendency, flowering point, seed setting, grain/ear count, thousand grain weight, stability and lodging tendency, threshability, etc.

A “functional fragment” of a nucleic acid molecule means a section of a nucleic acid molecule which has a functionality which is identical to or comparable with the total nucleic acid molecule from which the functional fragment derives. As such, the functional fragment may have a nucleotide sequence which, over a length of at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, 94% 96%, 97%, 98% or 99%, is identical to or homologous with the total nucleic acid molecule. A “functional fragment” of a protein means a section of the amino acid sequence of a protein which has a functionality which is identical to or comparable with the total amino acid sequence of the protein from which the functional fragment derives. As such, the functional fragment may have an amino acid sequence which, over a length of at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, 94% 96%, 97%, 98% or 99%, is identical to or homologous with the total amino acid sequence of the protein.

In the context of the invention, the term “homologue” should be understood to mean a protein of the same phylogenetic origin, the term “analogue” should be understood to mean a protein which exerts the same function, but is of another phylogenetic origin, and the term “orthologue” should be understood to mean a protein from another species which exerts the same function.

The term “hybridization” or “hybridizing” should be understood to mean a procedure in which a single-stranded nucleic acid molecule pairs to a nucleic acid strand which is as complementary as possible, i.e. base-pairs. Examples of standard methods for hybridization are described in Sambrook et al., Molecular Cloning: A Laboratory Manual 3rd Ed. Cold Spring Harbor Laboratory Press. Cold Spring Harbor, N.Y., 2001. Preferably, this should be understood to mean at least 60%, more preferably at least 65%, 70%, 75%, 80% or 85%, particularly preferably 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% of the bases of the nucleic acid molecule base-pair with the nucleic acid strand which is as complementary as possible. The possibility of such pairing depends on the stringency of the hybridization conditions. The term “stringency” relates to the hybridization conditions. High stringency is when a base pairing is made difficult, and low stringency is when base pairing is easier. The stringency of the hybridization conditions depends, for example, on the salt concentration or ionic strength and the temperature. In general, the stringency can be increased by raising the temperature and/or reducing the salt content. The term “stringent hybridization conditions” should be understood to mean those conditions in which a hybridization primarily takes place only between homologous nucleic acid molecules. The term “hybridization conditions” here relates not only to the conditions prevailing during actual pairing of the nucleic acids, but also to the conditions prevailing during the associated washing steps. Examples of stringent hybridization conditions are conditions under which, primarily, only those nucleic acid molecules hybridize which have at least 70%, preferably at least 75%, at least 80%, at least 85%, at least 90% or at least 95% sequence identity. Examples of stringent hybridization conditions are: hybridization in 4×SSC at 65° C. and then washing several times in 0.1×SSC at 65° C. for approximately 1 hour. The term “stringent hybridization conditions” used here may also mean: hybridization at 68° C. in 0.25 M sodium phosphate, pH 7.2, 7% SDS, 1 mM EDTA and 1% BSA for 16 hours and then washing twice with 2×SSC and 0.1% SDS at 68° C. Preferably, a hybridization is carried out under stringent conditions.

The term “interval” or “chromosomal interval” means a continuous linear section on a genomic DNA which is present in an individual chromosome in planta or on a chromosomal fragment and which is usually defined by indicating two markers which determine the end points of the interval on the distal and proximal side. In this regard, the markers which define the terminals of the interval may also be part of the interval. Furthermore, two different intervals may also overlap. In the description, an interval is specified by the indication “between marker A and marker B”. A terminal marker of an interval may also be located in a defined marker region to one side of the interval. A marker region is then defined by providing two flanking markers and constitutes a chromosomal section on which further markers can lie, in addition to the flanking markers. Flanking markers determine the end points of a marker region and are themselves part of the marker region. If two end markers of an interval are markers in different marker regions either side of an interval, then in the description an interval is specified by the statement “between a marker in a marker region X which is flanked by the markers C and D, and a marker in a marker region Y which is flanked by the markers E and F”.

The term “introgression” as used in the context of the present invention means the transmission of at least one desired gene allele to a genetic locus from one genetic background to another. As an example, an introgression of a desired gene allele at a specific locus can be transmitted to a descendant by sexual crossing between two parents of the same species. Alternatively, for example, the transmission of a gene allele may also occur by recombination between two donor genomes in a fused protoplast, wherein at least one donor protoplast carries the desired gene allele in its genome. In each case, the descendants, which then comprise the desired gene allele, are then back-crossed repeatedly with a line which comprises an excellent genetic background, and selected for the desired gene allele. The result is fixing of the desired gene allele in a selected genetic background.

The term “linkage drag” is used in general to describe the phenotypical expression of unwanted donor genes which reside in the same genomic region as the target QTL (Quantitative Trait Locus) and thus are closely coupled with it. As an example, this includes the observation that, by means of introgression of the chromosomal fragment which carries the restorer gene(s), donor genes which have a negative effect are transferred into the introgression line, so that the introgression line then performs less well for specific agronomic traits than the original recipient line.

In the case of restoration of male fertility, Rfp1-carrying introgression segments usually manifest linkage drag in the form of deleterious effects on the yield, i.e. grain yield and other properties such as plant height, grains per ears and thousand grain weight; see, for example, Hackauf et al., J. Kulturpfl. 61 (2009), 15-20; Hackauf et al., Molecular Breeding 30 (2012), 1507-1518.

The feature that in an inventive hybrid plant, a linkage drag otherwise coupled with the restoration property is reduced or (completely) eliminated, relates to the linkage drag which would otherwise occur in a hybrid plant (control plant). The control plant has in its genome a chromosomal segment on chromosome 4R with at least one interval from marker locus tc256739 to marker locus tc176835 from a donor selected from the group consisting of IRAN IX, Pico Gentario and Altevogt 14160. This is the same for the interval Xp15/55-Xscxx04 segment from IRAN IX; see Hackauf et al., Molecular Breeding 30 (2012), 1507-1518. Unless otherwise stated, alternatively or in addition, the term “feature that in an inventive hybrid plant, a linkage drag otherwise coupled with the restoration property is reduced or completely eliminated” should also be understood to mean the improvement in a property of the hybrid plant in accordance with the invention compared with a control plant. Thus, for example, this could be applied to an increased pollen shedding which results in the minimization of ergot infestation.

A “locus” is a position on a chromosome where one or more genes or one or more gene alleles can be found, which cause or influence an agronomic trait. In particular, “locus” here means the Rfp1 locus which restores the pollen fertility for the Pampa cytoplasmic male sterility (CMS).

The term “marker” describes a nucleotide sequence which is used as a reference or orientation point. A marker for detecting a recombination event should be suitable for monitoring differences or polymorphisms within a plant population. For markers, these differences are on the DNA level and, for example, are polynacleotide sequence differences such as, for example, SSRs (simple sequence repeats), RFLPs (restriction fragment length polymorphisms), FLPs (fragment length polymorphisms) or SNPs (single nucleotide polymorphisms). Markers may be derived from genomic or expressed nucleic acids such as, for example, spliced RNA, cDNA or ESTs and may also refer to nucleic acids which are used as probes or primer pairs and as such are suitable for amplification of a sequence fragment using a PCR-based method. Markers which recognize genetic polymorphisms between members of a population can be detected by means of established methods from the prior art (An Introduction to Genetic Analysis. 7th Edition, Griffiths, Miller, Suzuki et al., 2000). Examples of these are: DNA sequencing, PCR-based, sequence-specific amplification, detection of RFLPs, or detection of polynucleotide polymorphisms using allele-specific hybridization (ASH), detection of SSRs, SNPs or RFLPs. Moreover, methods for the detection of ESTs (expressed sequence tags) and RAPD (randomly amplified polymorphic DNA) are also known. Depending on the context, the term “marker” in the description may also mean a specific chromosomal position in the genome of a species where a specific marker (for example SNP) can be found. Such a marker position may be used in order to monitor the presence or absence of a coupled locus, for example a coupled locus which contributes to the expression of a specific phenotypical trait (for example Rfp1 or linkage drag). As an example, the marker locus may also be used in order to observe the segregation of alleles at a locus (QTL or individual gene) which is genetically or physically close-coupled with the marker position.

“Operatively connected” means connected in a common nucleic acid molecule in such a manner that the connected elements are positioned and/or orientated with respect to each other such that a transcription of the nucleic acid molecule can take place. A DNA which is operatively connected with a promoter is under the transcriptional control of that promoter.

Particle “organs” mean, for example, leaves, plant stem, trunk, roots, vegetative buds, meristems, embryos, anthers, ovulae, seeds or fruits, in particular seed grain. The term “plant portion” or “plant portions” includes, but is not limited to the plant stem or the stalk, leaves, flowers, inflorescences, roots, fruit and seeds as well as the pollen. Furthermore, plant “portions” means an aggregation of a plurality of organs, for example a flower or a seed, or a portion of an organ, for example a cross section through the plant stem. Examples of plant “tissue” are callus tissue, soft tissue, meristem tissue, leaf tissue, shoot tissue, root tissue, plant tumour tissue or reproductive tissue as well as the formative tissue, functional tissue (known as the parenchymal tissue), vascular tissue, strengthening tissue and covering tissue (known as the epidermis). However, the tissue is not limited to this list. The term plant “cells” should be understood to mean, for example, isolated cells with a cell wall or aggregates thereof or protoplasts.

In the context of the invention, unless stated otherwise, a “plant” derives from any dicotyledon, monocotyledon and gymnosperm species. Preferably, the plants are monocotyledon and are of importance in agriculture and market gardening or for the production of bioenergy (bioethanol, biogas, etc). Examples include Gossypium sp., Zea mays, Brachypodium distachyon, Triticum sp., Hordeum vulgare, Oryza sativa, Sorghum sp., Musa sp., Saccharum officinarum, Secale cereale, Avena sp., lawn and forage grass. A plant in accordance with the invention is preferably a plant from the genus Secale, in particular the species rye (Secale cereale).

The expression “resistance” or “resistant” to a pathogen should be understood to mean the resistance or defensive power of a plant or plant cell to the damaging influences of the pathogen and extends from inhibiting the development of disease to complete suppression of the development of the disease. As an example, the resistance of Rfp1-carrying hybrids to ergot is a resistance based on an “escape” mechanism: spores of the fungus are mechanically denied access to the gynoecium because of the fast-closing husks following fertilization by the pollen. A mediated resistance may be a newly-attained resistance or an increase in an already existing partial resistance. In connection with the present invention, a plant/plant cell is resistant or has a resistance to the pathogen ergot, i.e, a hybrid plant which exhibits an increased resistance to a pathogen, preferably against a fungus, in particular against the fungus Claviceps purpurea (Fr.).

The term “cereal plants” should be understood in particular to mean monocotyledon plants which belong to the gramineous order (Poales), preferably to the sweet grass (Poaceae) family. Examples in this case are plants which belong to the genuses Avena (yeast), Triticum (wheat), Secale (rye), Oryza (rice), Panicum, Pennisetum, Setaria, Sorghum (millet), Zea (maize) etc., preferably Hordeum (barley). Secale (rye), i.e. a Secale cereale, p. africanum, p. ancestrale, p. dalmaticum, p. kuprijanovii, p. montanum, p. silvestre, S.vavilovii plant, is particularly preferred.

A “transgenic plant” refers to a plant the genome of which has integrated into it at least one polynucleotide, preferably a heterologous polynucleotide. Preferably, the polynucleotide is stably integrated, which means that the integrated polynucleotide remains stable in the plant, is expressed and is also inherited in the descendants in a stable manner. The stable introduction of a polynucleotide into the genome of a plant also includes integration into the genome of a plant of the preceding parental generation, whereupon the polynucleotide can be further inherited in a stable manner. The term “heterologous” means that the introduced polynucleotide, for example, originates from a cell or an organism with a different genetic background from the same species or from another species, or is homologous to the prokaryotic or eukaryotic host cell, but is then localized in a different genetic environment and thus is different from a corresponding polynucleotide which is possibly naturally present. A heterologous polynucleotide may be present in addition to a corresponding endogenous gene.

The term “yield-reducing effect” should be understood to mean the phenotypical expression of a DNA sequence which is coupled or close-coupled with the target gene, in this case the restorer gene, and thus co-segregates. This is a frequent problem in backcrossing programs with exotic donors, namely the joint inheritance of desired and unwanted genes for the purposes of breeding described, for example, by Brinkmann et al., Crop Sci. 17 (1977), 165-168 and Tanksley et al., Bio/Technology 7, (1989) 257-264. This complex of the restorer gene and further unwanted genes, which are in part yield-reducing, has until now always been transmitted in part or in full into the breeding material, whereupon the introgression lines, for example, in addition to the advantageous restoration property, contain other negative traits which, for example, and depending on the location, bring about a significant reduction in yield. Correspondingly, linkage drag here is advantageously a negative yield effect which is connected with efficient restoration capability.

A reduction or alleviation of linkage drag occurs when its negative phenotypical properties as regards the control plant are only 0 to 75%, which corresponds to a reduction of 25-100%. In a preferred embodiment, the reduction is 50-100% or 75-100%. In a particularly preferred embodiment, the negative properties which are connected with linkage drag are almost completely or completely eliminated and the reduction in the linkage drag is between 90% and 100%. A reduction or alleviation of linkage drag for hybrid plants in particular may also mean a linkage drag effect on the yield of less than 7 dt/ha (quintals per hectare), less than 6.5 dt/ha or less than 6 dt/ha, preferably less than 5.5 dt/ha, less than 5 dt/ha, less than 4.5 dt/ha or less than 4 dt/ha, or most particularly less than 3.5 dt/ha, less than 3 dt/ha, less than 2.5 dt/ha or less than 2 dt/ha compared with a corresponding near-isogenic plant or hybrid plant which does not contain the inventive chromosomal segment or the inventive nucleic acid molecule. In order to quantify the linkage drag, the linkage drag effect can be standardized as a percentage of the performance of the NIB-E partner, as will be described below in Examples 1 and 2.

The term “vector” or “vector system” as used here in connection with genome editing refers to a transport means for introducing a recombinant construct comprising nucleic acids or even polypeptides as well as optional further sequences such as regulatory sequences or localization sequences, directly or indirectly into a desired target cell or target plant structure into the desired cellular compartment. Direct introduction is carried out into a target plant cell or target plant structure which contains nucleic acids which, in accordance with the present disclosure, are to be modified in a specific manner. Indirect introduction comprises introduction into a structure, for example cells of leaves or other plant organs or tissue which in fact are not of direct interest to the target plant cell, but wherein the systemic propagation and onward transmission of the vector comprising a recombinant construct in accordance with the present disclosure into the target plant structure, for example meristem tissue or cells or stem cells, is ensured. The term “vector” in the context of the transfection of amino acid sequences encompasses suitable agents for peptide or protein transfection such as, for example, ionic lipid mixtures or agents which are suitable for transfection of a nucleic acid, such as, for example, carrier materials by means of which nucleic acid and amino acid sequences can be introduced into a cell by bombardment with particles such as gold and tungsten particles, for example. Furthermore, this term also encompasses viral vectors, i.e. modified viruses such as, for example, those which derive from the following viruses: Barley Stripe Mosaic Virus (BSMV), Brome Mosaic virus (BMV), Maize yellow dwarf virus (MYDV) and bacterial vectors such as Agrobacterium spp., for example Agrobacterium tumefaciens. Finally, the term also encompasses suitable transport means for introducing linear nucleic acids (single- or double-stranded) into a target cell. The person skilled in the art in this field will be aware of other sequences which a vector must contain in order to be functional in a desired target cell. Conventional production, working-up and use of vectors of this type are also known to the person skilled in the art in this field.

The term “recombinant construct” as described herein in connection with genome editing refers to a construct comprising, inter alia, plasmids or plasmid vectors, cosmids, synthetic yeast or bacterial chromosomes (YACs and BACs), phagemids, bacteriophage vectors, an expression cassette, single-stranded or linear nucleic acid sequences or amino acid sequences, and viral vectors, i.e. modified viruses which can be introduced into a target cell in accordance with the present disclosure. A recombinant construct in accordance with the invention may comprise genome editing tools or parts thereof. As an example, CRISPR/Cas tools or parts thereof comprise at least one gRNA or at least one Cas nuclease variant and/or at least one further effector domain, either in the form of a nucleic acid or an amino acid sequence. TALENs tools or parts thereof comprise, for example, at least one TAL effector domain and/or at least nuclease variants, preferably a type II endonuclease such as FokI, for example. Furthermore, the recombinant construct may comprise regulatory sequences and/or localization sequences. The recombinant construct may be integrated into a plasmid vector and/or be isolated from a plasmid vector, for example in the form of a polypeptide sequence or a single or double-stranded nucleic acid not connected to a plasmid vector. After introduction, the construct is intrachromosomal or, as is preferable, extra-chromosomal and is not integrated into the genome and usually in the form of a double-stranded or single-stranded DNA, a double-stranded or single-stranded RNA or a polypeptide.

Embodiments and Implementations of the Present Invention Will Now be Described by Way of Example with Reference to the Accompanying Figures and Sequences:

FIG. 1: Genetic and physical map of the Rfp1 locus. A) High resolution genetic map of the Rfp1 locus on the long arm of the rye chromosome 4R. The numbers under the uppermost horizontal line describe the number of recombination events observed between the associated markers among 4563 individual test plants. Information regarding the marker codings are listed in Table 2. B) Rfp1-spanning contig of BAC clones from the Sce-B-R05104 library. C) Predicted genes on the Rfp1 locus. The bold boxes represent exons of functional genes or gene fragments, pseudogenes or mutated genes. The orientation of the genes is indicated by horizontal arrows. The vertical line in the mTERF gene 175019_c7 describes an early stop codon in the gene sequence. The abbreviations F and C indicate that for the marker concerned, a dominant restorer genotype specific for fertility (F) or a co-dominant inheritance (C) has been observed.

FIG. 2: Mapping of functional restorer genes on Rfp1 locus. With the aid of molecular selection markers, in two exemplary test series, recombinant individual plants with different lengths of donor chromosomal segments (D) were identified in the genetic background of a pollen parent line (E). The expression of the functional restorer genes Rfp1a and Rfp1b was determined in test crossing descendencies for each recombinant plant with the highly diagnostic male-sterile tester genotype Lo6-P(SR). Table 2 lists the marker haplotype of the NIB partner D which carries the donor introgression segment. AE-D: difference between the means of test crossings from NIB partners which each homozygously carry the elite allele (E) or the donor allele (D). This difference in the mean over 7 locations determines the linkage drag effect for grain yield absolutely in dt/ha and as a percentage of NIB partner E. LSD5%: limiting difference, 5% level of significance.

FIG. 3: Mapping of restorer gene Rfp1b. From 13 recombinant plants, the allele of the donor genotype IR9 could be unambiguously determined between the markers P20 and 7_01_H_1441 at the marker locus 72F13_c2_mTERF in 4 plants. The Rfp1b phenotype was detected in test crossing descendencies of the recombinant genotypes with the CMS tester Lo6-P(SR) and matched perfectly with the marker genotypes of the mitochondrial transcription tERmination factor (mTERF) mapped by means of 72F13_c2_mTERF [A=homozygous carrier of elite allele; H=heterozygous carrier of elite or donor allele; Rfp1b*=Rfp1 or elite phenotypes were detected using the pollen shedding of respectively 15 individual test crossing descendants of the recombinant genotype and the highly diagnostic tester from Lo6-P(SR).]

FIG. 4: Shows the linkage drag effect for grain yield (Δ_(E-D)) for the introgression segment 455 and 765 (y-axis), plotted against the mean linkage drag effect for each of the seven locations (x-axis). The recombinants with the short introgression segment 455 exhibited a low linkage drag effect, and the recombinants 765 with the long introgression segment exhibited a large linkage drag effect. It was also clear from the experimental data that the linkage drag effects for the seven environments were very different. Clearly, adverse weather conditions during the shooting phase were responsible for the stress conditions.

FIG. 5: Production of test crossing seed with Near-Isogenic Bulk partners as the pollen parent and CMS “single cross” tester T911 as the female parent. The use of NIB partners (NIB pairs) is shown in isolation parcels which acted for seed production from test crossing seed. In this regard, NIB partners dusted a CMS “single cross” tester which represented the opposing heterotic pool. Seed which was harvested on the CMS testers was then sown in field experiments with multiple environments in order to determine the linkage drag effect phenotypically.

FIG. 6: Expression cassette in the vector pYFrfp1 containing the restoration gene rfp1b (SEQ ID NO: 1) under the control of the ubiquitin promoter from maize with the first intron and nos-terminators.

FIG. 7: Comparison of the nucleotide sequence of the wild type rfp1a gene (“Wildtyp-rfp1a”) (SEQ ID NO: 32) with the nucleotide sequence of the rfp1a gene from IRAN9 (“Iran9_rfp1a”) (SEQ ID NO: 28).

FIG. 8: Comparison of the nucleotide sequence of the wild type rfp1b gene (“Wildtyp-rfp1b”) (SEQ ID NO: 30) with the nucleotide sequence of the rfp1b gene from IRAN9 (“Iran9_rfp1b”) (SEQ ID NO: 1).

FIG. 9: Comparison of the amino acid sequence of the wild type rfp1a protein (“Wildtyp-rfp1a”) (SEQ ID NO: 33) with the amino acid sequence of the rfp1a protein from IRAN9 (“Iran9_rfp1a”) (SEQ ID NO: 29).

FIG. 10: Comparison of the amino acid sequence of the wild type rfp1b protein (“Wildtyp-rfp1b”) (SEQ ID NO: 31) with the amino acid sequence of the rfp1b protein from IRAN9 (“Iran9_rfp1b”) (SEQ ID NO: 2).

The following examples illustrate the invention without in any way limiting the subject matter of the invention. Unless stated otherwise, standard methods were employed.

EXAMPLES Example 1: Exemplary “Near Isogenic Bulk”—Development of Rye Line 455 in Lo310 Background

As can be seen in FIG. 5, for all recombinant genotypes, NIB D and E partners were produced in which bulks each of more than 100 BC₆S₁ plants, which were homozygous carriers or non-carriers of the Rfp1, were outcrossed with the single cross CMS tester T911. Boundary isolation walls ensured that no foreign pollination occurred. The test crossing seed produced in this manner was then used in field trials in multiple environments. Test crossing plants were verified for the correct pedigree by (i) subsequent marker analysis and (ii) evaluation of the pollen shedding in the field trials. All of the evaluated test crossing plants which were generated from the NIB D partners exhibited full pollen shedding, while those which originated from the E partners exhibited a very significantly reduced and only partially restored male fertility.

Example 2: Field Trials

The yield evaluation trials were carried out at locations with different environmental conditions. Thus, for example, in 2012, there were seven locations in Germany (D) and Poland (PL). As can be seen in Table 1, the locations were selected so that they represented agricultural conditions in Central Europe with, additionally, different stress conditions (drought stress and nitrogen deficiency). In the low nitrogen regime, nitrogen was applied in quantities which were substantially below the usual doses. In an unwatered trial, natural precipitation constituted the only source of water, while in the watered trials, an additional quantity of water of approximately 25 mm per week was applied. In this manner, it was possible to measure effects of the Rfp1 introgression segments in very different environments. The results were then used (1) to determine the introgression segment-specific linkage drag effect, (2) to identify introgression segments with high environmental stability, and (3) to identify diagnostic environments which make the linkage drag discernible to a greater extent.

TABLE 1 Description of the trial locations and the applied treatments in 2012 Ground Precipitation Agronomic Location State points mean [mm] regime BEK D 51 769 KON PL 55 581 local agricultural practice BBG D 93 469 KO2 D 43 769 low nitrogen KO3 D 43 769 not watered PET_I D 28 636 watered PET_N D 28 636 not watered (BEK = Bekedorf (Lower Saxony); KON = Kondratowice (Lower Silesia); BBG = Bernburg (Saxony-Anhalt); KO2 and KO3 = Bergen (Lower Saxony); PET_I and PET_N = Petkus with watering (I) and nitrogen variants (N) (Brandenburg); Ground points: index measuring the quality of an area of farmland. The scale of possible values extends from 1 (very poor) to 100 (very good).)

A “split plot” trial design was used for all environments. The main plots used the test crossings of the recombinant BC₆S₁ lines. The subplots were the respective near-isogenic D and E bulk NIB pairs. The “NIB D partner” was the homozygous carrier of the donor introgression segment, while the “NIB E partner” was the homozygous carrier of the corresponding elite line segment. The corresponding D and E partners were sown directly adjacent to each other in order to minimize environmental differences and thus to be able to measure the differences due to the introgression segment with more accuracy. Trial units of the yield experiments were the test crossings from 7 BC₆S₁ lines, which themselves represented four different haplotypes. As an example, the results for the recombinant with the shortest introgression segment (455) are shown compared with that with the longest introgression segment (765) in detail. The latter is already significantly shorter than the segments which are currently available for hybrid varieties which have already been approved.

The preparation and implementation of the field trials were in accordance with the general rules and are well known to the person skilled in the art. The statistical analysis of the data was carried out in two steps: firstly, at each individual location, a variance analysis was calculated for all repeats with the aim of determining the accuracy of the trial and to determine respective location-specific yield averages for the recombinant lines and their introgression segments. In a second step, said averages were then used for the analysis regarding the environments.

Drastic and statistically significant differences (t-test) for the linkage drag effect were detected, for example, between the recombinant genotypes 455 and 765. As can be seen in FIG. 2, the linkage drag effect averaged over the locations (Δ_(E-D)) was 3.7 dt/ha for haplotype 455, while it was nearly twice that (7.0 dt/ha) for haplotype 765. The differences between the two recombinants manifested themselves particularly clearly at location PET_N under high stress due to spring drought. Here, the linkage drag effect (Δ_(E-D)) for recombinant 765 rose to 18 dt/ha, while it remained at only 3 dt/ha for haplotype 455. At another location (BBG) under moderate stress conditions, the linkage drag effect (Δ_(E-D)) dropped to 11 dt/ha for the haplotype 765, which, however, was a multiple of that shown by haplotype 455 with only about 3 dt/ha. Fundamentally similar relationships were found in the experiments carried out in 2014. Here again, shortening of the introgression segment corresponded to a reduction in linkage drag for yield. In order to be able to compare the experiments in 2012 and 2014 with each other, it was recommended that the linkage drag effect be standardized as a percentage of the performance of the NIB partner. FIG. 2 illustrates that the linkage drag for the recombinants with the shortest introgression segments (1120 and 455) were only between 3.9% and 4.7%, while the recombinants with the longest introgression segments (1110 and 765), with 6.2% and 7.1%, suffered substantial performance losses. However, the yield reductions cited latterly are still relatively small when set in context, i.e. currently known introgression segments which contain the two markers tc256739 and tc300731 cause linkage drag effects of more than 10%.

The locations differ in their diagnostic value for detection of linkage drag (see FIG. 4). Means for Δ_(E-D) over all tested introgression segments in 2012 (Series 018/2012) were from 3.2 (PET_I), 3.3 (KON), 4.1 (KO2), 4.6 (BBG), 5.7 (Ko3), 6.7 (BEK) to 10.0 (PET_N) dt/ha. The smallest mean linkage drag effect was observed in the watered trials in Petkus (PET_I), in which the availability of water was not limited. In contrast, the unwatered trials in the same macro-environment (PET_N) were very strongly influenced by drought in the pre-flower phase. It can be seen (FIG. 4) that the segment from 765 reacted significantly to environmental stress (regression coefficient on the mean linkage drag effect: 1.6 dt/ha). In contrast to this, the segment from 455 exhibited a very high environmental stability which could be confirmed in the PET-N stress environment.

Example 3: Identification of Recombinant Genotypes

In order to identify recombinant genotypes and in order to describe the respective remaining introgression segments, the following markers were used: ctg24, ctg32, ctg16b, P20, c40745, wherein the marker P20 played the most significant role in all of the subsequent studies. From a publicly available rye BAC library developed from cv. Blanco, which is not a carrier of the Rfp1 gene (Shi B J, et al. (2009): Physical analysis of the complex rye (Secale cereale L.) Alt4 aluminium (aluminum) tolerance locus using a whole-genome BAC library of rye cv. Blanco. Theor Appl Genet. 119(4):695-704), and with the aid of marker P20, BACs could be identified as a source for further marker sequences. It was possible to isolate and sequence a highly promising BAC. This opened up the possibility of providing a BAC library of restorer gene-carrying genotypes (denoted here as “IR9” or ROS104), which can be viewed with specific DNA probes using PCR. Although no Rfp1 locus-spanning BAC contig could be produced, the locus flanking BAC clones could be identified with the aid of this library. Multiple marker combinations could be designed using the sequences: see Table 2. These were used for the selection of new recombinants and partially converted into a new marker system (SNP-based).

Furthermore, with the aid of the investigations with mTERF, a novel Rf gene could be identified which until now has not been described as being of relevance to fertility restoration for any plant species. For the first time it has been shown that at the 4R introgression segment, two standalone and also equal-valued Rf genes are effective having regard to restoration.

With the aid of close-flanking markers and a phenotyping test, for both Rf genes involved, it could be shown that the respective donor introgression segments could be made even smaller and the restoration capability could be maintained in full.

Example 4: Development of Close-Coupled Markers

In order to develop close-coupled markers for the Rfp1 locus in rye, as well as in order to isolate the functional restorer gene, a Rfp1 allele from the exotic breed IRAN IX was used as the most efficient source of fertility restoration. Bound up with this very efficient restoration performance, however, is a linkage drag which can cause a significant reduction in yield, depending on the respective location.

In addition to the close-coupled marker P20, for fine mapping of the Rfp1 region, further proximal close-coupled markers were provided. Essentially, this was carried out using two strategies which enabled one recombinatorily shortened genomic interval per molecular marker to be selected and thus, finally, to enable the unwanted linkage drag to be identified and reduced.

1) The first strategy is based on the exploitation of conserved synteny between rye and Brachypodium as well as rye and barley. In this manner, novel close-coupled markers were derived using gene information from the two cited model grass/cereals varieties. 2) The second strategy starts from the assumption that the close coupling of the marker P20 also indicates a close physical coupling, and is based on the chromosome walking method. This means that, by means of close-coupled markers, a freely available rye BAC library was searched (population variety “Blanco” (Shi et al., Theor Appl Genet 119 (2009), 695-704), in order to produce an initial BAC contig as the starting point for a contig analysis of the Rfp1 locus. For this, a newly established BAC library of the restorer gene-carrying genotype (described here as “IR9” or ROS104) could be viewed with specific DNA probes using PCR.

With the aid of these libraries, BAC clones could be identified from which new markers could be derived which finally authorized selection of a smaller interval about Rfp1.

Example 5: Mapping of New Markers in the Population ROS13024-BC1 and Identification of Two Independent but Equivalently-Acting Loci for the Restoration Property (Rfp1a and Rfp1b)

As a supplement to the marker P20, in the context of the present invention, individual new markers suitable for selection were developed on the basis of the isolated BAC clones from the ROS104 BAC library. The markers obtained using the isolated bac clones were used for high resolution mapping in advanced breeding material, whereupon finally, the target interval could be further resolved. The mapping of these markers in the target interval as well as relative to the target gene was carried out in multiple experiments on internally developed, splitting populations. The markers and associated primer sequences, with the aid of which the loci for the restoration property could be identified in plants, are summarized in Table 2 below.

With the aid of the newly established selection markers, surprisingly, for the first time it was possible to show, in the mapping studies that were carried out, that the restoration property can be associated with two independent but closely coupled and almost equivalently acting restorer genes (Rfp1a and Rfp1b) at the Rfp1 locus (FIG. 1). In addition, it was shown that one of the Rf genes involved, namely the Rfp1b gene, is a gene which codes for an mTERF protein. In addition, Rfp1a has a very high sequence agreement with and can most probably be denoted as an mTERF gene. Because until now it was not known that such a gene was relevant in cereals for fertility restoration and/or pollen shedding, this result was completely unexpected.

As a consequence, with the aid of the present invention and the associated experiments, it has been shown for the first time that two independent and also almost equally-acting Rf genes having regard to restoration are located in the 4R introgression segment. Moreover, these two genes can now, for example with the aid of the markers described in this invention, also be separately evaluated for breeding purposes and can be used separately or in combination with each other. Thus, one aspect of the present invention concerns the use of the Rf gene Rfp1a alone or in combination with Rfp1b. In a further embodiment, the Rf gene Rfp1b may be used independently of Rfp1a. Preferably, both of the equivalently acting loci cited above lead to a restoration of fertility.

TABLE 2 Marker overview (Tm = melting temperature; *described in Hackauf et al, 2012) Forward Reverse Product primer (5′-3′) primer (5′-3′) Tm size Marker ID Derived from BAC [SEQ ID NO] [SEQ ID NO] [° C.] [bp] Performance Category tc256739* Barley EST 21 22 60 200/300 codominant COS #1: ctg32 541014 contig32 16 17 60 371 fertile pool gene based specific STS #2: ctg24met2a5 541O14 contig24 14 15 60 1148  codominant gene based STS #3: ctg2 541014 contig2 4 5 60 221 codominant ISBP #4: ctg16b 541014 contig16 10 11 60 516 codominant gene based STS #5: c40745_1 SceAssembly02 18 19 60 675 codominant gene based STS #6: P20 72F13 contig2 6 7 65 424 fertile pool gene based specific STS #7: 72F13_c2_mTERF 72F13 contig2 8 9 68 475 fertile pool gene based specific STS #8: 7_01_H_1441 72F13 contigl 12 13 60 480 fertile pool STS specific tc300731* Wheat EST 23 24 55 340/300 codominant COS

In one of the experiments which were carried out (Ro14037), almost 5000 individual plants of a BCxS1 population were genotyped. In this regard, a genetic polymorphism between the Rfp1 donor chromosomal segment and the pollen parent line Lo727 could be detected. The genetic fingerprint produced on the basis of this marker enabled a reliable identification to be carried out of only approximately 20 plants which could be characterized by recombination in the region of the valuable Rfp1 gene variant. In this manner, the genetic interval around Rfp1 in the genetic background of the line Lo727 was defined by the flanking markers ctg2 and 7_01_H_1441, for which a genetic separation of approximately 0.2 cM or approximately 120 kb could be calculated (FIG. 1). The genetic map produced documented that the target interval around Rfp1 could be resolved in the desired manner with the aid of the newly developed marker. Firstly, the first gene-based markers as well as the marker c40745_1 were used for selection on the genetic background of an elite pollen parent genotype. The marker P20 was employed to detect the segment with the restorer gene Rfp1. In a test series (018/2012), it was then possible to observe the expression of Rfp1 and, connected with it, the complete restoration of male fertility for different lengths of Rfp1 introgression segments (bottom of FIG. 2) using test crossings with the male stamp CMS tester Lo6-P(SR).

This discovery proves (1) coupling between Rfp1 and P20, as well as (2) the value of the developed selection marker for recombinatorial reduction of the donor chromosomal segment.

Building on this result, in further experiments (for example Ro12011), further cleaving BCx families were initially genotyped with the marker P20. In an experiment denoted test series 12-1-23, approximately 3200 individual plants were identified which inherited pure for the allele for the elite line Lo310. With the gene-based markers defined above, 4 recombinant plants with different lengths of Rfp1 introgression segments were identified in this material group (top of FIG. 2). In test crossings with these 4 lines as well as the control genotype #1058 without Rfp1 donor segment with the male-sterile CMS tester Lo6-P(SR), the expression of Rfp1 could be observed in 3 entirely male-fertile descendants of the lines 1110, 1039 and 1120. The genetic constitution of the recombinants led to the conclusion that a further, independent and equivalently acting restorer gene was located in the region of the target interval. This restorer gene coupled with the ctg2 marker was denoted Rfp1a, while the restorer gene coupled with P20 was given the notation Rfp1b (see also FIG. 1).

For the exact localization of the restorer gene Rfp1b, additional mapping experiments were carried out (for example Ro13030). In analogous manner to the experiments above, BCx interval plants in which the donor chromosomal segment had already been recombinatorially shortened with the aid of the gene-based marker from BAC clone 541014 were initially genotyped with the marker P20. In this manner, almost 4300 genotypes were identified which inherited pure for the elite allele of the pollen parent line Lo310 at this marker gene site. With the aid of the marker 7_01_H_1441, for example, a total of 13 recombinants to marker P20 could be detected in this material group (FIG. 3). In 4 of these 13 recombinants, the donor allele from the genetic source could be observed at the marker locus 72F13_c2_mTERF. For 3 of these 4 recombinants, test crossing descendants were established in which the male fertility had been completely restored. In contrast, the test crossing descendants of the 9 carriers of the non-restorer marker allele of mTERF exhibited a completely male-sterile phenotype.

By matching the observed phenotypes with the marker genotypes of a mitochondrial transcription tERmination factor (mTERF), it was possible to calculate a genetic separation between P20 and Rfp1b of r=0.094 cM. This recombination estimate was in very good agreement with the recombination estimate of r=0.011 cM calculated for the earlier experiments between P20 and the mTERF gene.

Example 6: Rfp1 Contig Production with the Aid of the BAC Library ROS104

BAC clones selected from the ROS104 BAC library acted as the basis for the development of probes and primers to continue the chromosome walking. An approximately 350 kbp contig was derived in this manner. By means of the markers and the mapping thereof in the advanced breeding material, it was shown that this contig carried markers which flanked the two restorer loci (FIG. 1 and Table 2).

Experiments showed that there was no PPR protein-coding gene in this interval, but in it there were 3 so-called mTERF (mitochondrial transcription termination factor) genes or gene fragments which were therefore clearly to be seen as candidate genes for Rfp1.

On the basis of the earlier work, a BAC contig of the Rfp1 locus in the background of a restorer genotype (elite inbred line Lo310 from the pollen parent pool) was constructed and the presence of two Rf genes was demonstrated by analyses of recombinant descendants.

Example 7: Validation of Results

In addition to the detection of the identified Rfp1b gene by genetic recombination in Example 5, the functionality of the gene was also tested in a transgenic approach. To this end, the protocol for Agrobacterium tumefaciens-mediated rye transformation by Herzfeld (2002. Development of a genetic transformation protocol for rye (Secale cereale L.) and characterisation of transgene expression after biolistic or Agrobacterium-mediated gene transfer. Dissertation, IPK, Germany) was used. To this end, donor plants from the inbred line L22 were cultivated in a greenhouse at approximately 20° C. with 16 h of light up to the flowering point, and then immature caryopses were surface-sterilized and immature embryos were prepared. These were placed with the scutellum side uppermost onto callus-inducing medium (containing MS salts (Murashige and Skoog, 1962. “A revised medium for rapid growth and bio assays with tobacco tissue cultures.” Physiologia plantarum 15.3: 473-497.), 100 mg/l caseine hydrolysate, 500 mg/l glutamine, 30 g/l saccharose, 2.5 mg/l 2.4-D, pH 5.8, 3.0 g/l phytagel) and pre-cultivated in darkness at 25° C. over a period of 5 days before transformation. For the purposes of the transformation, following earlier precultivation, the immature embryos were placed on 6× microplates (Greiner Cellstar) and suspended in 10 ml of liquid callus-inducing medium. For the osmotic treatment, the liquid medium was exchanged against 10 ml of osmotic medium (containing MS salts (Murashige and Skoog, 1962), 100 mg/l caseine hydrolysate, 500 mg/l glutamine, 30 g/l saccharose, 6.0 mg/l 2.4-D, 72.9 g/l mannitol, pH 5.8) and the explants were plasmolysed over a period of 4-6 h.

Next, the osmotic medium was removed again and the calluses were inoculated with approximately 300 μl of agrobacterium suspension. Next, a vacuum treatment at 500 mbar was carried out over one minute followed by an incubation for 10 min. The explants were washed twice in 10 ml of infection medium (containing MS salts (Murashige and Skoog, 1962), 100 mg/l caseine hydrolysate, 500 mg/l glutamine, 15 g/l saccharose, 15 g/l glucose, 6.0 mg/l 2.4 D, pH 5.2, 200 μM acetosyringone) and co-cultivated overnight at 22° C. After 14-16 h, the explants were again washed several times in infection medium and finally transferred to solid co-cultivation medium (infection medium supplemented with 3.0 g/l phytagel), keeping the scutellum side directed upwards. The explants were cultivated for two more days and then transferred to solid callus-inducing medium which had been enriched with 150 mg/l of timentin to inhibit the growth of agrobacteria.

After 14 days, the calluses were transferred onto selective regeneration medium (containing MS salts (Murashige and Skoog, 1962), 100 mg/l caseine hydrolysate, 500 mg/l glutamine, 30 g/l saccharose, pH 5.8, 5.0 g/l agarose type I, 150 mg/l timentin, 30 mg/l paromomycin). After a further three weeks, the calli were transferred into suitable cultivation receptacles which contained selective regeneration medium with 50 mg/l of paromomycin sulphate for shoot lengthening.

The vector pYFrfp1 (FIG. 6) containing the restoration gene rfp1b (SEQ ID NO: 1) under the control of the ubiquitin promoter from maize with the first intron and the 35-S terminator inserted into the vector pPZP111 were introduced by electroporation (Mersereau et al., 1990. “Efficient transformation of Agrobacterium tumefaciens by electroporation.” Gene 90.1: 149-151) into the agrobacterium strain AGLO (Lazo et al., 1991. “A DNA transformation-competent Arabidopsis genomic library in Agrobacterium.” Nature Biotechnology 9.10 (1991): 963-967). An AGLO (pYFrfp1) culture was cultivated overnight in 50 mg/l LB medium to saturation (OD660 2-2.5). 2 ml was centrifuged at 5000 rpm for 5 min and the pellet was dissolved in 1 ml of LB medium as well as 1 ml of infection medium. Prior to infection of the implants, the bacteria were incubated for approximately two hours (OD660 1.5-2.0).

In order to analyse the tDNA, the binding region of the tDNA border and the rye genome was amplified using inverse PCR (Ochman et al., 1990. “Amplification of flanking sequences by inverse PCR.” PCR protocols: A guide to methods and applications: 219-227). To this end, the DNA of the transgenic rye plants was digested with BamHI or BglII, circularized with T4 DNA-Ligase and then used as the template for the PCR. The amplification was carried out in the context of a nested PCR with the GeneAmp-PCR System 9700 (Perkin Elmer). The reaction conditions corresponded to those recommended by the manufacturer, wherein 200 ng of template DNA was used in the first reaction and 0.5 μl from the first reaction was used as the template for the second reaction, so that the final volume was 25 μl.

For the right border (RB) for the first reaction (28 cycles at 94° C. for 30 s, 48° C. for 60 s and 72° C. for 2 min), the following primers were used: RB1R 5′-CTG AAT GGC GAA TGC TAG AGC AG-3′ (SEQ ID NO: 25) (LacZ region) and UBIF 5′-CTG CAG TGC AGC GTG ACC CG-3′ (SEQ ID NO: 26) (3′ region of maize ubiquitin promoter). For the second reaction (32 cycles at 94° C. for 30 s, 52° C. for 60 s and 72° C. for 2 min) the following primers were used: RB2R 5′-CGT TTC CCG CCT TCA GTT TAA AC-3′ (SEQ ID NO: 27) and UBIF primer. PCR amplification products with blunt ends were obtained in which two DNA polymerase was added to the second reaction mixture. These amplification products were cloned into the PCR vector (Invitrogen, San Diego, Calif.) and then a sequence analysis was carried out on it.

Successfully transformed rye plants were propagated and crossed with Pampa male sterile inbred lines. Descendants which carried and expressed the restoration gene rfp1b as a transgene exhibited a restoration of male sterility.

As an alternative to the transgenic approach described above, the gene function can also be produced by knockout of the restoration gene in a restorer line. To this end, the person skilled in the art could, for example, also employ TILLING or genome editing (for example TALENs or CRISPR/Cas) in order, for example, to introduce an early stop codon into the coding sequence or to displace the reading frame by insertion/deletion. The result would be a non-functional mTERF protein and a loss of restoration capability.

Example 8: Characterization of Plant Material with Regard to Pollen Shedding

The above results now enable a plant breeder to use the desired restoration for Pampa CMS together with an excellent pollen shedding in the development of new cereal plants, in particular rye and barley. During the course of this, negative agronomic traits on the yield have been significantly reduced and the risk of ergot infestation has simultaneously been minimized. The degree of pollen shedding which is obtained with a male pollen parent in accordance with the invention can be determined on a scale of 1 to 9 (Geiger H H, Morgenstern K (1975) Angewandt-genetische Studien zur cytoplasmatischen Pollensterilitat bei Winterroggen [Applied genetic studies on cytoplasmic pollen sterility in winter rye]. Theor Appl Genet 46:269-276). In this regard, values of 1 to 3 mean non-dehiscent, empty anthers with a small amount of degeneration; values of 4 to 6 indicate a partially removed male sterility with <10% to >50% fertile anthers; values from 7 to 8 denote pollen-shedding anthers with increased anther size; and a value of 9 corresponds to a completely male-fertile plant like that expected in normal cytoplasm. Test crossings produced plants in accordance with the invention which had a value of 7 or higher, preferably even a value of 8 or higher or, almost regularly, a value of 9.

In Germany, ergot susceptibility of new rye varieties has been tested in field trials with artificial inoculation over several years and in different locations. The evaluation of the ergot susceptibility in this regard is based on a score system of 1 (very slightly susceptible) to 9 (very strongly susceptible). As can be seen in Table 3, hybrid varieties which carry a restoration gene from the donors IRAN IX, Pico Gentario or Altevogt 14160 (#1-#4), because of the excellent pollen shedding, exhibit a significantly reduced infestation with ergot pathogens (Claviceps purpurea).

TABLE 3 Stages of expression for ergot susceptibility for four hybrid varieties which carry restoration genes for the donors IRAN IX, Pico Gentario or Altevogt 14160 (left hand half; #1 to #4) and for four hybrid varieties with other restoration systems (right hand half). Hybrid varieties which carry restoration genes from donors Hybrid varieties with IRAN IX, Pico Gentario or other restoration genes Altevogt 14160 Value or restorationsystems Value Visello 3 SU Drive 6 Minello 4 SU Forsetti 5 Palazzo 4 SU Performer 6 KWS Bono 4 SU Mephisto 6

In the context of the particular harvest results, the MRI (Max Rubner-Institut, Bundesforschungsinstitut für Ernährung and Lebensmittel [Federal Research Institute for Nutrition and Foodstuffs]) regularly collates ergot infestation data from the rye harvest in German agriculture. An evaluation of this data shows that the occurrence of ergot can be more than halved if, instead of hybrid varieties with a stage of expression of 5 to 6, varieties are used which, with a stage of expression of 3-4, are significantly less susceptible as regards ergot.

Example 9: Structural Comparison of rfp1a and rfp1b on a DNA and Amino Acid Level

Structural comparisons of rfp1a and rfp1b on a DNA (Table 4) and amino acid level (Table 5) show a comparatively high agreement between non-restoring wild type and restoring IRAN9. Surprisingly, however, rfp1a and rfp1b from IRAN9 exhibit a very low agreement with only 76% on a DNA level and only 66% or 68% on a protein level, although both have a restoration-mediating action. This shows that the tendency of mTERF proteins to restore male fertility is possible over a wide structural variability.

TABLE 4 Comparison of identities of cDNAs of rfp1a and rfp1b rfp1a rfp1b Wild type Iran9 Wild type Iran9 rfp1a Wild type — 97% 76% 76% Iran9 — 76% 76% rfp1b Wild type — 95% Iran9 —

TABLE 5 Comparison of identities of cDNAs of rfp1a and rfp1b rfp1a rfp1b Wild type Iran9 Wild type Iran9 rfp1a Wild type — 96% 67% 68% Iran9 — 66% 67% rfp1b Wild type — 90% Iran9 —

Example 10: Detection of Restoration Capability of rfp1a and rfp1b Genes Alone and in Combination as Well as from Different Sources

Table 6 clearly shows that test crossing plants which are equipped with only one copy, rfp1a or rfp1b, have a slightly smaller but on the whole entirely sufficient pollen shedding and anther size when compared with plants which have both copies.

TABLE 6 Anther score, according to Geiger & Morgenstern (1975), of test cross plants (Tx . . .) with different rfp1 copy configurations: Mean of restored test cross plants rfp1 copy Anther Test crosses configuration Anther score length (mm) TxBC7(Lo310) 1120 rfp1a 8 7 TxBC7S1(Lo310) 3308 rfp1a 8 7 TxBC6S1(Lo310) 455 rfp1b 8 7 TxBC6S1(Lo310) 217 rfp1a and rfp1b 9 8 TxBC6S1(Lo310) 765 rfp1a and rfp1b 9 8 TxBC4(Lo316xIRAN IX) rfp1a and rfp1b 9 8 TxBC2(Lo316xAltevogt) rfp1a and rfp1b 9 8 TxLo310 (original line) — 3 

1-19. (canceled)
 20. A plant of the genus Secale suitable, as a male pollen parent, for restoring the pollen fertility for the Pampa cytoplasmic male sterility (CMS), wherein a) in the plant or in a hybrid plant from a cross with a female CMS parent, a linkage drag effect on the yield otherwise coupled with the restoration property is less than 7 quintals per hectare (dt/ha) compared with a corresponding near-isogenic plant or hybrid plant which does not contain the chromosomal segment or the nucleic acid molecule as defined in b), and b) the plant comprises a chromosomal segment which has at least one introgressed nucleic acid molecule which is capable of mediating the restoration property, and the at least one introgressed nucleic acid molecule has a nucleotide sequence which is selected from the group consisting of: (i) a nucleotide sequence comprising SEQ ID NO: 28, (ii) a nucleotide sequence which codes for the amino acid sequence of SEQ ID NO: 29, (iii) a nucleotide sequence which is complementary to a nucleotide sequence in accordance with (i) or (ii), (iv) a nucleotide sequence which has an identity of at least 99% with the nucleotide sequence in accordance with (i) or (ii), (v) a nucleotide sequence which codes for an amino acid sequence which has an identity of at least 99% with SEQ ID NO: 28, and (vi) a nucleotide sequence which codes for an amino acid sequence which, compared with the amino acid sequence shown in SEQ ID NO: 29, exhibits discrepancies in the amino acid sequence in the form of conservative amino acid mutations.
 21. The plant as claimed in claim 20, wherein the chromosomal segment is an interval between the marker loci tc256739, ctg32 or ctg24met2a5 and tc300731 or 7_01_H_1441 on chromosome 4R from a donor selected from the group consisting of IRAN IX, Pico Gentario and Altevogt
 14160. 22. The plant as claimed in claim 20, wherein the chromosomal segment has one or more of the following marker loci of the donor: ctg2, P20, 72F13_c2_mTERF or ctg16b.
 23. The plant as claimed in claim 20, wherein the chromosomal segment is characterized by the absence of one or more of the following marker loci of the donor: 7_01_H_1441, ctg24met2a5 or ctg32.
 24. The plant as claimed in claim 20, wherein the chromosomal segment is no larger than 190 kb.
 25. The plant as claimed in claim 20, wherein the plant is an inbred plant, a plant, a double haploid plant or a hybrid plant.
 26. The plant as claimed in claim 20, which has an enhanced resistance against a pathogen.
 27. A seed or descendant of the plant as claimed in claim 20, wherein the seed or the descendant comprises the chromosomal segment.
 28. An organ, plant portion, tissue or cell of the plant as claimed in claim
 20. 